When you launch the game on your mobile / tablet for the first time, you will directly be asked if you want to connect to Facebook or play as a guest.
Just tap "Connect to Facebook" and you will automatically be synchronized with your Facebook account.
If you play as a guest, you can always connect to Facebook by accessing the main menu (button at the upper-left corner) and tapping the "Connection" button.
Then simply hit the "Connect to Facebook" button and the game will automatically be synchronized with your Facebook account.