Pure rookie here, let me try to help.
you can use a bitmap,jpg,tga,png that I know of. You use the template you painted for the game, just like how you import it, thats why I always choose tga. When the scene opens, press the M button and that will bring up your materials screen. Choose the eye dropper and click it on the car in the scene. It should bring up Chevy,Ford, etc etc. somewhere in the panel. Click on that and you should see the plain paint that is in the scene. Click on that and you can select your file to be rendered.
It's easy for me to do but hard to explain, I don't have max installed anymore.
