How to sign up to XBox Live?

I went out and bought a 50 foot cat5 and a 3mo subscription card for XBox Live and hooked it all up but I can't figure out how to get online. It asks me to select a gamer tag then input my life story then it wants a credit card #. I purchased the 3mo card so I wouldn't have to give my #. The card has a hexa # and the letter keys on the card# input screen are disabled so does anyone know what I am doing wrong? My boy wants to kill me so help please.
Cmdr Chill

 

Taken from http://www.xbox.com/en-US/live/gettingstarted101.htm

Hope it helps!

 

Thank You OverCooked for the link. I was able to enter my card # on a manage accounts page from that link. My problem was I was trying to do it through the XBox. I guess it might be possible to do that but it's a moot point now. The boy is online now and my life is no longer in danger, Thanks Again!