Add a button to your xaml page as shown below:

<Grid x:Name="LayoutRoot" Background="White" >
<Button Width="100" Height="50" x:Name="showPopup"
Click="showPopup_Click" Content="Show Popup" />
</Grid>

Add the following code to your code behind file (page.xaml.cs)

Popup p = new Popup();
private void showPopup_Click(object sender, RoutedEventArgs e)
{
   // Create a panel control to host other controls
   StackPanel panel1 = new StackPanel();
   panel1.Background = new SolidColorBrush(Colors.Gray);

   // Create a button
   Button button1 = new Button();
   button1.Content = "Close";
   button1.Margin = new Thickness(5.0);
   button1.Click += new RoutedEventHandler(button1_Click);

   // Create a text label
   TextBlock textblock1 = new TextBlock();
   textblock1.Text = "The popup control";
   textblock1.Margin = new Thickness(5.0);

   // Add text label and button to the panel
   panel1.Children.Add(textblock1);
   panel1.Children.Add(button1);

   // Now, make the panel a child of the popup so that
   // the panel will be shown within the Popup when displayed.
   p.Child = panel1;

   // Set the position.
   p.VerticalOffset = 25;
   p.HorizontalOffset = 25;

   // Show the popup.
   p.IsOpen = true;
}

void button1_Click(object sender, RoutedEventArgs e)
{
   // Close the popup.
   p.IsOpen = false;
}

Now run the application. You can see the page with a button. When you click on the button, a popup layer will appear with a text label and a button in it. When you click on the button in the popup, it will close the popup.