You decide which dealership you will use and the Concierge contacts them with the exact numbers. After you sign off on the configuration, options and paint, the Concierge tells the dealership what your amount is and sends them a copy of your exact build sheet with numbers. You go into dealership, write and sign check (or whatever money payment you arrange), get receipt and then wait for car to be built. For the GT it was 5-6 months until delivery after that.
When car is ready for delivery, Concierge contacts you and dealership on exact delivery time and date. You are expected to complete payment a few days before actual delivery. They delivered mine on a Sunday morning. The dealership opened up and furnished coffee and donuts. About 100 people there, my friends and family, dealership employees, technicians, etc.