How to texturize OBJ elements?

I am currently trying to import a Revit model into Unity to demonstrate what the building will look like to clients. I exported the Revit model into Rhino, added textures in Rhino, and then exported the model into Unity as an OBJ. The problem I am having is getting textures to show up on the OBJ model. I am able to colorize the elements; however, I am having a hard time texturizing them. If I slap a dirt texture on a wall, the wall will turn brown but it doesn't have the texture of dirt. Can anyone explain to me how I can make this work?