Yep, you just do it on the Apple Store app or apple.com. They usually will have the option for you to do pre-approve to get a head start (*must need iPhone to do this). From my experience last year, the Apple Store App on the idevice were more reliable then going to apple.com on your desktop on launch day as the one from the idevice was more reliable and was open right at pre-order start. Last year if I remember, the apple.com on desktop wasn't open till maybe 1-2 minutes after the pre-order start time.