I'm always keen to help newcomers, but what you're asking can't be explained in just a few minutes. Not sure also what's your specific problem. Is the car already mapped and you just created a skin and want to see it in Max? Then change the WWCARBODY material and assign your new skin to it.
If not and you're starting from a scratch made car then it requires a basic knowledge about 3DS Max and how gMotor2 material works.
Not sure if you're familiar with Max, and how rF cars have to be defined, so follow my advice if you aren't:
if you're new to Max then learn the basics: how to use the interface, create basic shapes, etc. You have some good YouTube videos about that in this same forum (take a look to the sticky located in this modeling section).
If you already know about that go to www.simraceway.com and watch the developer videos. I know many people don't like simraceway at all, but the developer videos (as well as other dev resources located there) are very good. I have learnt valuable things there. The ones about materials will help you to understand how gMotor2 materials work in 3DSMax.
There are more tutorials on internet. Take a look to Virtua_LM's ones, for example.
Be patient. It's not that hard as it looks.
Hope this will help in some way ;)