the easiest thing to do is go to www.jailbreakme.com in your safari from the iphone and scroll jail break ...u will have cydia in the iphone. In cydia add  the repository repo666.ultrasn0w.com to unlock the phone (make sure to turn off 3gs if u are going to use with T-mobile after jilbreaking) its a piece of cake these days....let us know if any confusion :)