The kiosk was very easy. You just go downstairs to the car rental area on the first floor of the terminal. The kiosks are near where you would enter the line for the counter. Just swipe the CC you used on the reservation, or enter your confirmatin #. Follow the directions on the screen and a receipt will print (takes about 2 minutes max). Walk over to the garage and follow the signs to Alamo, then find the aisle for the size car you reserved. You pick any vehicle in the aisle. Make note of any damage to the vehicle. Drive toward the exit and present the receipt you just printed, along with your driver's license to the attendant. Alamo Insiders get their spouse as add'l driver for free, so give both DL's to the attendant. Tell the attendant about any damage to the vehicle and they will note it on the account.
We were surprised to be driving out of the airport garage about 30 minutes after landing, including a bathroom stop and picking up two checked bags.