For iOS binding and recovery:
How do I sync my account to Game Center?
Step 1: Make sure you are logged into game center by going to Setting, tapping Game Center and tapping your account at the top.
Step 2: Simply start Underworld Empire. Any time you start up the game your account will automatically be synced to Game Center.
How do I retrieve my account using Game Center?
Step 1: Go to the \"More\" tab by clicking the gears on the bottom left of the game's home screen.
Step 2: Click the option that is titled \"Character Transfer.\"
Step 3: Find and tap your desired account."