How to texturize individual elements of a mesh?

Hello, I am currently trying to texturize individual elements of an OBJ model I exported from Rhino. All of the exterior walls are in a mesh. When I try to texturize an exterior wall, all of the other exterior walls receive the same texture/color. This is often times helpful; however, my chimney is classified as an exterior wall as well and I would like to make it have a different texture/color than the rest of my exterior walls. Is there a way to texturize an element in a mesh without texturizing the entire mesh?