You can connect to Facebook in the Menu by tapping the "Facebook" button. Fill in your Facebook information as usual, and you will be connected! This will save your game to allow you to move it to other devices, and lets you play socially in machines with multiplayer mechanics.
If you have a previous saved game attached to that account, you will be prompted to pick data. Select "Facebook Save" to keep your saved data - THE DATA NOT SELECTED WILL BE DELETED.