How to add checkbox control in XAML

Hi,

I want to add Checkbox control in Xaml page. I added below code in .Xaml page.

    <CheckBox Margin="10, 10, 3, 3" 
                  Name="acceptPolicy" 
                  Content = "Accept our policy"
                  FontSize="12" 
                 Checked="CheckBox_Checked"/>

But i am getting below error?

Error CS0246: The type or namespace name 'CheckBox' could not be found (are you missing a using directive or an assembly reference?)

I am new to Xaml, since i am unable to find Checkbox control in Xamarin.Forms Xaml, i tried to use default Checkbox from here.

If some controls doesn't exist in Xamarin.Forms Xaml, whether can i use default Xaml controls or not?