You can place your order before you arrive either from USTAD Mobile Apps or by calling 1-844USTAD US. If you pre-order or make a reservation, you still must call after you collect your luggage to let the dispatcher know you are ready.
Or, if you do not pre-arrange a ride, just call when you have all luggage and your taxi will be at the middle lane in about 10 minutes.
Taxis are staged in a lot on the outskirts of the airport.