From LAS airport you have to walk outside from the baggage claim, to take a shuttle (about 7-minutes) to the car rental center.
Upon arrival, National is the first stand to your left.
Luckily they sent me an email about my car being ready and I didn't have to go to the counter. I took the escalator up to the second floor and was greeted by a customer service agent. They said pick any car in the midsize lane.
We got into the car and drove towards the exit where another agent checked license and paperwork. Easy!
Before returning the car, I received another email about how to do the express drop off. I ended up following the signs in the car rental center which lead me to the normal drop off but it was quick and painless. We repeated the steps and took the shuttle back to the terminal.
I would rent from National again!