What is the simplest way to implement remote push notifications in a PCL project?

If this should be in "Cross-Platform", lemme know, We just think there's more about PCL projects in relation to Xamarin.Forms.

Is there any working examples we can refer to for the client-side implementation?
This documentation is great, but it doesn't explicitely explain where to put the provided code which is essential for a beginner like me.

http://developer.xamarin.com/guides/cross-platform/application_fundamentals/notifications/android/remote_notifications_in_android/

PS: The documentation has many missing images and the lists are messed up.

The server-side and Google Cloud Messaging parts are complete, but the client-side is confusing in a Xamarin PCL project context. We assume that this can only be done using platform-specific code for now, sadly.