I was looking for the same thing. I found this website from Mircorsoft which has steps to add in authentication to your Android app.
https://www.windowsazure.com/en-us/develop/mobile/tutorials/get-started-with-users-android/
This link starts the intro to Mobile services for Android
https://www.windowsazure.com/en-us/develop/mobile/tutorials/get-started-android/