Ive imported a material to use on one of my walls, but i need a different material applied to its other surfaces. In UDK i can just click on a surface and apply a new material
how can i do that in Unity? I've searched all over and found nothing.
UDK has a nice tool to create levels with constructive solid geometry, which includes UV mapping adding materials to different surfaces.
Unfortunately Unity does not have anything similar, so I suggest you create the level geometry in a 3D modelling program (Blender, 3D Max, or any other).