its actually very easy..
extract the zip file to you .../tremulous/base folder.
open the pk3 file and inside are 2 folders. 1 is called models, the other scripts.
extract them out of the pk3 into ur base folder. Its going to ask u if u want to replace the already exsiting folders, or w/e a mac says, say yes.
Open GTKRadiant, open ur map, right click where u want it to be on your map, goto misc -> misc_model
a screen should pop up, navigate to .../tremulous/base/models/mapobjects/wmlight and select the .md3 file and hit open and your done.
I've actually downloaded all those models that guy has
