Apple iPad For iOS 4.3 - Manual (Page 133)

Other players may invite you to play the game.
Respond to an invitation to play a game: Tap Accept or Decline in the alert
that appears.
You can disable multiplayer games in Restrictions. See “Restrictions” on page 158.
You can prevent other players from inviting you to play games by turning off Allow
Game Invites in Game Center settings. See “Your Status and Account Information” on
page 135.
Return to Game Center: Press the Home button, then tap Game Center on the
Home screen.
You can also press the Home button twice quickly and choose Game Center from your
recent apps.
Leaderboards
Some games provide one or more leaderboards to show the ranking of the game’s
players, with their scores, times, or other measures of the players’ success.
See a game’s leaderboard: Tap Games, then choose the game and tap Leaderboard.
You may also be able to view leaderboards from within a game.
If a game has variations (such as Easy, Normal, and Hard), the Categories screen lets
you choose the leaderboard for the game in general, or for one of the variations.
The leaderboard shows the ranking of your friends, and of all players. You may be able
to view leaderboard stats for a specific time period, such as today, this week, or all time.
Rotate iPad to see a leaderboard in landscape orientation.
Start playing a game from the leaderboard: Tap Play in the upper-right corner.
133 Chapter 20 Game Center