DemoProb/DemoProb/MainWindow.xaml

<Window x:Class="DemoProb.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:DemoProb"
        mc:Ignorable="d"
        Title="Леарн" Height="450" Width="800"
        Icon="SchoolLog/school_logo.ico" 
        FontFamily="Comic Sans MS"
        FontSize="20">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="0.1*"/>
            <RowDefinition Height="0.2*"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Button x:Name="BackNavigation" Style="{StaticResource ButtonNavigation}"  Content="&#xE72B;" Click="BackNavigation_Click"/>
        <Button x:Name="Recorder" Style="{StaticResource ButtonMain}" Content="Ближайшие записи" HorizontalAlignment="Right" Click="Recorder_Click" Visibility="Collapsed" Margin="10,0"/>
        <Frame Grid.Row="2" Name="FrameWindow" NavigationUIVisibility="Hidden"/>
        <StackPanel  Grid.Row="1">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <TextBlock Text="Пароль для режима администратора" HorizontalAlignment="Center"/>
                <PasswordBox x:Name="Password" Width="200" Margin="0,5" Grid.Row="1"/>
                <Button x:Name="SignIn" Content="Войти" Width="200" Style="{StaticResource ButtonMain}" Click="SignIn_Click" Grid.Row="2"/>
            </Grid>
        </StackPanel>
    </Grid>
</Window>