there's probably tutorials somewhere but lets c if i can remember..!!
Add your material/texture in material editor first then to map objects onto faces switch to object faces mode, and select [select single] in SEL mode. Then select the faces u want to map [should turn red], if you want the bonnet mapped use top view or doors then which ever side view. Then select your texture/material for those faces' attributes [ctrl A i think for attributes] So now ur faces know which texture to use u gotta map em.
Think it's Surface, mapping, assign UV in object faces mode with ur faces selected in red.. change any view except the view ur textures are facing i.e not the one u assigned ur material to - to UV mapper view and then right click anywhere in the view where u assigned ur attributes. Then all the faces that were selected should appear in the UV mapper view. Switch to object mode and turn SEL mode off, then reshape the faces in UVmapper view to fit the texture in that view. ZM uses tga for materials so if you save a tga as hi_bonnet convert it to tex and rename to hi_bonnet_1. Bizarre i know, just remember xxx.tga = xxx_1.tex.........
Lot of stuff there, hope it helps - when i started using it i got no help at all until i stumbled accros a tutorial which is no longer available!! GLuck