diff --git a/composeApp/build.gradle.kts b/composeApp/build.gradle.kts
index dd68fbd..bf6b3bc 100644
--- a/composeApp/build.gradle.kts
+++ b/composeApp/build.gradle.kts
@@ -15,8 +15,7 @@ plugins {
 
 
 kotlin {
-    @OptIn(ExperimentalWasmDsl::class)
-    wasmJs {
+    js {
         moduleName = "composeApp"
         browser {
             val projectDirPath = project.projectDir.path
@@ -58,6 +57,7 @@ kotlin {
 
         commonMain.dependencies {
             implementation(libs.banking.client.model)
+            implementation(libs.fints4k.banking.client)
 
             implementation(libs.kcsv)
             implementation(libs.klf)
diff --git a/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/dialogs/AddAccountDialog.kt b/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/dialogs/AddAccountDialog.kt
index bf16470..4f4de4e 100644
--- a/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/dialogs/AddAccountDialog.kt
+++ b/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/dialogs/AddAccountDialog.kt
@@ -6,12 +6,16 @@ import androidx.compose.material.*
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Close
 import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.compose.ui.window.Dialog
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 import net.codinux.banking.ui.forms.*
 import net.codinux.banking.ui.model.BankInfo
 import net.codinux.banking.ui.service.Colors
@@ -32,6 +36,11 @@ fun AddAccountDialog(
         derivedStateOf { selectedBank != null && loginName.length > 3 && password.length > 3 }
     }
 
+    var isAddingAccount by remember { mutableStateOf(false) }
+
+    val coroutineScope = rememberCoroutineScope()
+
+
     Dialog(onDismissRequest = onDismiss) {
         RoundedCornersCard {
             Column(Modifier.background(Color.White).padding(8.dp)) {
@@ -93,10 +102,35 @@ fun AddAccountDialog(
                     Spacer(Modifier.width(8.dp))
 
                     TextButton(
-                        onClick = onDismiss,
-                        enabled = isRequiredDataEntered
+                        modifier = Modifier.width(150.dp),
+                        enabled = isRequiredDataEntered && isAddingAccount == false,
+                        onClick = {
+                            selectedBank?.let {
+                                isAddingAccount = true
+
+                                coroutineScope.launch { // TODO: launch on Dispatchers.IO where it is available
+                                    val errorMessage = DI.bankingService.addAccount(selectedBank!!, loginName, password)
+
+                                    withContext(Dispatchers.Main) {
+                                        isAddingAccount = false
+
+                                        if (errorMessage == null) {
+                                            onDismiss()
+                                        } else {
+                                            // TODO: show error Message
+                                        }
+                                    }
+                                }
+                            }
+                        }
                     ) {
-                        Text("Hinzufügen")
+                        Row(verticalAlignment = Alignment.CenterVertically) {
+                            if (isAddingAccount) {
+                                CircularProgressIndicator(Modifier.padding(end = 6.dp))
+                            }
+
+                            Text("Hinzufügen")
+                        }
                     }
                 }
             }
diff --git a/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/service/BankingService.kt b/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/service/BankingService.kt
index d35d572..2ce5264 100644
--- a/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/service/BankingService.kt
+++ b/composeApp/src/commonMain/kotlin/net/codinux/banking/ui/service/BankingService.kt
@@ -2,8 +2,12 @@ package net.codinux.banking.ui.service
 
 import bankmeister.composeapp.generated.resources.Res
 import kotlinx.datetime.LocalDate
+import net.codinux.banking.client.SimpleBankingClientCallback
+import net.codinux.banking.client.fints4k.FinTs4kBankingClientForCustomer
 import net.codinux.banking.client.model.AccountTransaction
 import net.codinux.banking.client.model.Amount
+import net.codinux.banking.fints.config.FinTsClientConfiguration
+import net.codinux.banking.fints.config.FinTsClientOptions
 import net.codinux.banking.ui.model.BankInfo
 import net.codinux.csv.reader.CsvReader
 import net.codinux.log.logger
@@ -33,6 +37,29 @@ class BankingService(
         return transactions
     }
 
+    suspend fun addAccount(bank: BankInfo, loginName: String, password: String): String? {
+        try {
+            val config = FinTsClientConfiguration(FinTsClientOptions(true))
+            val client = FinTs4kBankingClientForCustomer(bank.bankCode, loginName, password, config, SimpleBankingClientCallback { tanChallenge, callback ->
+                // TODO: show EnterTanDialog
+            })
+
+            val response = client.getAccountDataAsync()
+            response.data?.let { accountData ->
+                if (cachedTransactions == null) {
+                    cachedTransactions = accountData.bookedTransactions
+                } else {
+                    cachedTransactions = (cachedTransactions!! + accountData.bookedTransactions).sortedByDescending { it.valueDate }
+                }
+            }
+
+            return response.error?.internalError ?: response.error?.errorMessagesFromBank?.joinToString("\n")
+        } catch (e: Throwable) {
+            log.error(e) { "Could not add account for ${bank.name} $loginName" }
+            return e.message
+        }
+    }
+
     private suspend fun readTransactionsFromCsv(): List<AccountTransaction> {
         val csv = Res.readBytes("files/transactions.csv").decodeToString()
         val csvReader = CsvReader(hasHeaderRow = true, reuseRowInstance = true, skipEmptyRows = true).read(csv)
diff --git a/gradle.properties b/gradle.properties
index 93239c3..98924f5 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -8,4 +8,7 @@ android.nonTransitiveRClass=true
 android.useAndroidX=true
 
 #Kotlin Multiplatform
-kotlin.mpp.enableCInteropCommonization=true
\ No newline at end of file
+kotlin.mpp.enableCInteropCommonization=true
+
+# Compose Multiplatform Web
+org.jetbrains.compose.experimental.jscanvas.enabled=true
\ No newline at end of file
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 76b03fb..5d68080 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -26,6 +26,7 @@ junit = "4.13.2"
 
 [libraries]
 banking-client-model = { group = "net.codinux.banking.client", name = "banking-client-model", version.ref = "banking-client" }
+fints4k-banking-client = { group = "net.codinux.banking.client", name = "fints4k-banking-client", version.ref = "banking-client" }
 
 kcsv = { group = "net.codinux.csv", name = "kcsv", version.ref = "kcsv" }
 klf = { group = "net.codinux.log", name = "klf", version.ref = "klf" }
diff --git a/settings.gradle.kts b/settings.gradle.kts
index e7673d6..a10d6cc 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -25,6 +25,10 @@ dependencyResolutionManagement {
             }
         }
         mavenCentral()
+        mavenLocal()
+        maven {
+            setUrl("https://maven.dankito.net/api/packages/codinux/maven")
+        }
     }
 }