How to Add Tile Icon in win 8 app development?

How to Add Tile Icon in win 8 app development?

i start learning win 8 app development m a beginner in win 8 app
development and m making and app and want to add its tile icon like when
we press window key then our program exe icon show as default but i want
to add my own icon ? how to do this .... plz tell me how to add image in
this code ? this is just an example of my code :
x:Class="Calculator.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Calculator"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="Tomato">
<Button x:Name="btn0" Content="0" HorizontalAlignment="Left"
Height="64" Margin="458,459,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn1" Content="1" HorizontalAlignment="Left"
Height="64" Margin="458,390,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn2" Content="2" HorizontalAlignment="Left"
Height="64" Margin="583,390,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn3" Content="3" HorizontalAlignment="Left"
Height="64" Margin="708,390,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn4" Content="4" HorizontalAlignment="Left"
Height="64" Margin="458,321,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn5" Content="5" HorizontalAlignment="Left"
Height="64" Margin="578,321,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn6" Content="6" HorizontalAlignment="Left"
Height="64" Margin="708,321,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn7" Content="7" HorizontalAlignment="Left"
Height="64" Margin="458,252,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn8" Content="8" HorizontalAlignment="Left"
Height="64" Margin="583,252,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<Button x:Name="btn9" Content="9" HorizontalAlignment="Left"
Height="64" Margin="708,252,0,0" VerticalAlignment="Top" Width="120"
FontSize="36" FontWeight="Bold" Click="showbtn"/>
<TextBox x:Name="Output" HorizontalAlignment="Left" Height="68"
Margin="458,179,0,0" TextWrapping="Wrap" VerticalAlignment="Top"
Width="370" FontSize="24"/>
</Grid>