I imported an object with many faces and materials, but I only want some materials to apply to certain faces, how could I do this? When I add the material, it adds it to the entire thing, how do I do it for one face?
This is actually pretty easy to do; first, go into Edit Mode, by pressing Tab, and select the faces on which you want the material to apply.
Then, go to the Properties panel, and in the Material tab, with the material you want selected on the list above, press Assign.
Notice that you can also select/deselect the faces corresponding to a material, by pressing the respective button.