QueenOfCoach

I will give you very specific instructions.

As you stand on the sidewalk, outside the Terminal 4, facing the terminal, you will be facing South. To your left is the 405 freeway (East) and to your right is the ocean (West).

You will see a small door that says Flagship or something similar. That is the door that takes you in to the small Flagship check-in room, as described above. I can't see you qualifying for Flagship flying a domestic LAX to Las Vegas. So, don't go in that door.

To the right of the Flagship door are the regular glass doors that go into the main terminal. All doors go into the same large area. Inside this large area, to the East (405 freeway, near the Flagship room) are the counters that handle Priority check in, such as domestic First Class. That would be you. There is a sign attached to the ceiling, near the glass door, that says "AA Priority".

Farther to the West (to the ocean) are the Main Cabin check in areas.

It really doesn't matter which door you use to enter the terminal. It's all one really large area. Just go in whatever door you like, where your ride drops you, and then turn to your left and make your way to the far East (towards the 405 freeway) end of the terminal. There you will see signage that says Priority Check in. After checking in, turning in your checked luggage and getting your boarding pass, they will direct you to the short escalator that leads to Priority TSA checkpoint. That escalator is at the far East (towards the 405 freeway) end. There is a guard at the foot of the escalator who will check your ID and boarding pass before letting you go up. At the top of the escalator, turn right with everyone else and go into the TSA Checkpoint queues. The queue for those with Pre-Check is to the left. The queue for those without Pre-Check is to the right. There should be someone there to guide you if you are unsure.

If you end up in a Main Cabin check in line, no worries. Your bags will still get on the plane and so will you. You'll just stand in line a bit more.

Finally, I'll mention the FlyAway. I live in North Los Angeles County and I really like the Van Nuys Flyaway. There are other Fly Away buses from Union Station, Westwood, etc.

You can buy one-way or round trip FlyAway tickets. When returning from LAX, they do not check tickets on the bus. Everyone just gets on and they get going. When you get to the destination (Van Nuys, Union Station, etc) they check your existing ticket or you can buy a ticket from a kiosk. It's all very efficient. I tell you this so you don't think you need to get your ticket or money ready when you get on the bus at LAX. You board the departure near the Green signs just outside baggage claim.

I can leave my car at the FlyAway in Van Nuys, or get dropped off. Then I am on the bus to LAX and am dropped right at the terminal, without the hassle of parking, or dealing with traffic. The FlyAway bus is a great deal. You mentioned you are new to travel, so I thought I would pass on that tip.