GameCenter login alert

Question

In a game I am developing using GameCenter, I want to handle the following scenario:

1. the user starts up the game. He is shown the system alert that prompts him to

Answer 1

May be the link will helpful (First three paragraphs): http://developer.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/GameKit_Guide/Users/Users.html#//apple_ref/doc/uid/TP40008304-CH8-SW9

The main point is in a rectangle "Important".