If you want to play the same farm on different devices, make sure it is attached to a Game Center ID or a Facebook ID.
To attach the farm to Facebook, launch the Facebook app on your device and make sure you are logged in with the correct Facebook account. Then launch the game, tap on the settings icon (top left corner of the screen) and tap on the button "Facebook – connect".
To attach the farm to Game Center, enter your Device settings and open Game Center, log in with your username and password (or create a new user if you haven’t done it yet), then launch the game. You should now see the "Welcome back, _username_" message from Game Center every time you launch the game, and this means the farm is correctly attached to the Game Center ID.
For more clear instructions on how to connect your game to Game Center, please go to our tutorial video section and select save your progress with Game Center.