Importing a downloaded tree into Unity 3D

I downloaded a tree that supposedly will work in Unity 3D. It consists of a folder with a .mtl file, .obj file, and a maps sub folder containing a bark.tga file and a leaves.tga file. Can I import this into Unity 3D and if so, how do I go about doing it?

Simply drop or copy those files and the folder into the Assets/ folder of your Unity project.

More information here.

OK, I did that, but now how do you get the tree to work with Terrain, Place Trees? I tried choosing Edit Trees and picked the tree from the asset menu, but when I place the tree on the scene, nothing shows up.