As PPs have said, as long as you have printed out your eTicket, you can go straight to the gate. They will exchange your print-out for a temporary ticket (it'll be one the standard credit card sized tickets that they issue). You can use that during the day, but you will eventually need to go to one of the ticket booths to exchange that for your actual AP. Once you have that, you will need to find a Photopass photographer and have your photo taken (unless you already have one in the system from a past AP).