ConfigWindow.xaml

<Window x:Class="wagtail.ConfigWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Configuration" Height="200" Width="300"
        Background="#222222">
    <Grid>
        <TextBox Name="ApiKey"
                 Foreground="White"
                 Width="200" Margin="10,10,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" Text="Enter API Key" GotFocus="TextBox_GotFocus" LostFocus="TextBox_LostFocus"/>
        <TextBox Name="VoiceId" 
                 Foreground="White"
                 Width="200" Margin="10,50,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" Text="Enter Voice ID" GotFocus="TextBox_GotFocus" LostFocus="TextBox_LostFocus"/>
        <Button Content="Save" Width="100" Margin="10,0,0,10" HorizontalAlignment="Left" VerticalAlignment="Bottom" Click="OnSaveClick"/>
    </Grid>
</Window>