Texture Mapping?

[FerrariMan]

I know nothing - literally nothing - about texture mapping and it's what's bothered me the most about not being able to make actual edited cars for NFSHS. For example, let's say I made a spoiler in ZModeler on top of EA's BMW Z3. These new polygons will not have any textures, so how do I make them? Another example is adding two  polygons to make a potential Mercedes symbol on an S Class mod based off the EA M5. How could I make those polygons mapped to the mercedes symbol in my texture file?

Someone please help