Boolean modifier issues.

So I imported a model from Team Fortress 2, as an SMD, and removed all the bones and such. I also optimized the model a little to be simpler, but there’s too much clipping so I need to use the boolean modifier to fix it.
See, there’s the little object list on the modifier. When I click it, the mesh doesn’t show up, but instead this bone object thing called smd_bone_vis. How do I get it to work with my mesh?

Thanks in advance,