You create your order on the app, customizing as you see fit, and then place your order. You now have until the end of the day to get to the Taco Bell you ordered from. When you get there, you tap one of two buttons to signify you've arrived and inform them to make your order (take out or drive thru) I usually check in when I'm still a few blocks away so my food is ready by the time I arrive. If you go inside, you just wait for them to call your name. If you go drive thru you just tell them "I'm picking up a mobile order for _________." Payment is handled via the app so you just grab your food and bounce. The free Doritos taco offer seems to have ended (at least in my area)