I guess you must be new. Once the auction is over you go back into the auction. At the top of the page it has a place with the address you set you Listia account up with. You will put a check in the little circle and hit send. Listia will notify me of your address and then I will send it to you.
@CR11: the 4G has a camera and is slightly thinner and longer than the 2G, but I don't even think I've actually ever seen a 3rd Gen iTouch. anyways, probably not for 4G because of the camera in the back, unless you don't care about that.