I have an app, and I'd like to add a share button to it. Once the button is clicked, I'd like it to open the following window:

Then the user will choose where to share it and it will display the following default message:
"Just found this great app! Find it here:http://www.windowsphone.com/en-us/store/app/amtrak/c8824bb8-3a85-48f7-af54-954bd5673cc6"
Can you please tell me how to do it?