First things first, you need a mod that can delete objects (no, not a performance mod). I have linked one below, but I'm pretty sure other object removing mods work too.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2696126057
Next, you will need a vehicle with wheels. Any vehicle will work, but for this guide, I am going to use the Crownzygot XVC.

Now that you have the required, use the remover tool to delete any tires that are on the vehicle. This is fairly easy, and should take only a few seconds.

Enjoy your hover car! Wheels are what move vehicles. The tires you deleted were just the visible form of the wheels. Have fun with this!

You are going to need the Physics Gun (Physgun) for this step of the tutorial.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2400310320
If you want your vehicle to look more like a hover car, then this is the spot for you. For this part of the tutorial, I am going to use the Castanet 500L GT. In my opinion, it is the best car to use, as its overall design adds to the hover car effect. First, delete the wheels (of course). Then, use the Physics Gun to set the car into the air. Freeze the car using RMB (right mouse button).
Now, add vehicle thrusters underneath the fenders. Try to be as accurate as possible when placing them. Depending on how the thrusters are placed and the conditions of the vehicle, it might actually fly off the ground.

Now that it is taken care of, you can continue driving your car as you normally would. Well, maybe. Just don't floor it if your car actually flies.

That is the end of the tutorial, unless somebody comes up with another way to make hover cars cooler.