Get started. Open Game Center. If you see your nickname at the top of the screen, you're already signed in. Otherwise, you'll be asked for your Apple ID and password.

Get some games. Tap Games, then tap a recommended game. Or browse for games in the App Store (look for Supports Game Center in the game details). Or get a game one of your friends has.

Play! Tap Games, choose a game, tap in the upper right, then tap Play.

Sign out? No need to sign out when you quit Game Center, but if you want to, go to Settings > Game Center and tap your Apple ID.