do you need to use the game center login?

part12studios

I am trying to get GC to work and it seems like if i have a link to a "game center" button.. which calls on the "show leaderboard" it effectively seems to bring up a login prompt..

my thought was that rather than make login in a manual process, it be automatic IF they click a game center button in the main menu.. however since i've had poor luck getting GC to work at all.. I just wasn't sure if i have to conform to a certain method...

Thanks
Caleb