Gotcha, go to the
F7 menu, vehicles and choose a vehicle to spawn! Assigned vehicles are vehicles that the devs have messed with the balance of, or added outright. These are the ones you'll actually race with, so in general you should look at these but some of your old favorites may not be added yet! If so, check unassigned and see if you can find it.
Once you've selected the car you want, you'll be inside your brand new car! Customization is pretty simple, both the
F5 menus support ways to make your car look the way you want it to. Just like with your character, when you feel your car has reached peak cool just go in the
F7 menu and save it. Now, whenever you spawn that car instead of getting just any lousy car, you'll get YOUR car, and that's way better. Plus, if you have a car saved rather than having to run and find it you'll just start in it which is a whole lot easier. If your beautiful, custom car ever gets damaged, spawn it in again and it'll be fresh and new like you want it to be.
Also, before you leave the server remember to type
/dv in the chat and despawn your car. Worst case scenario, your car could be left right in the middle of a racetrack and make it harder for people to race! Or it could just lag up the server a bit. Regardless, be polite and recycle your cars to protect the environment. (Also do this to any abandoned cars you see, it's a huge help and people will like you if you do this)