Its exactly like Emerald Club. You just get your luggage, take the elevator up to the main level and follow the signs to the rental cars outside, across the street; you do not need to go to the counter. Then follow the signs to National Rental Cars. Then look for the sign for the aisle of the size of car you reserved.
Pick a car. The keys are in it. Load it up and then head to the booth. Give them your CC and license and then you are off.