After you get your luggage, walk out the front and you'll see a low rise building to your right. That's the rental car building, however National is offsite so don't bother looking for their booth. The queue for the shuttles is actually behind this building. Take a right between the two buildings and you'll see a canopied area where you can wait for the National shuttle.

After a short drive, the driver will ask if there's any Emerald Aisle folks. He'll direct you to a booth outside which will handle your paperwork.