If you plan on being in the infield, you should have registered online. But its probably too late to pre register. So when you get there, you just register your car under NICO car club. Then if will have to enter in a particular area for the car show. If you don't play on entering your car in the infield, park outside in whatever designated area and buy a ticket to get in. You can go over to the NICO invasion over Atlanta thread and read up on what alot of people are going to be doing.
zerothread/190426
This is the meet and greet thread. There is a caravan thread also. I'm sure you can just email mail somebody that is going and see when and where you could meet up with them. I would email Maxhopper and he should be able to give you all the info you need for their caravan.