It's very easy. Just go down to level 1 in the airport and go out the doors across from the rental counter and cross the street (crosswalk). If you are on side A, you have to take an escalator up to the second level of the garage. If you are on side B, it's on ground level. Just look for National signs. Once you get inside the garage and find the National area, you will see green signs on the poles designating the size of cars for that row. You want to look for Emerald Aisle. Then just pick a car from that row, the keys will be in it. Drive to the exit, there will be a booth. At the booth, give them your license, credit card and the hang tag from the mirror (Emerald Aisle should be checked off on it). I also give them a copy of my reservation, but I don't think it's required. They will give you a paper back, confirm the price. Then drive off!