Here are Zynga's insctructions exactly:
Have you removed RewardVille yet from your Zynga games? If not, what do you like about the system? Sound off in the comments. Add Comment.If you feel you still want to disable RewardVille functionality, go to www.RewardVille.com. Make sure you are logged in. (If you see your photo, name, and RewardVille statistics on the top right of the RewardVille screen, you are logged in; if you don't see them, click the "Log in with Facebook" icon in the upper right to log in.) After logging in, at the bottom of the page, you will see an option for "Preferences". Click that, then check the box that says, "Turn off RewardVille on my game bar." The next time you restart your game, RewardVille will be removed from the top of your games. Should you want to rejoin the RewardVille program, you can re-activate the zPoints bar at any time by reversing this process.