A censer is a container in which the incense you make is burned. Charcoal is very hot when it burns and a wooden anything isn't a good idea. The censer can be metal, like those you see in Catholic churches, or it can simply be a bowl filled with sand. Until you find a censer that you personally like, you can just use a bowl half-filled with sand or salt. The sand/salt protects the bowl and the surface it sits on against heat.
My personal censer looks like an Alladin lamp, and I got it at a nearby hippie store. It's my favorite!