To add to neiro`s comments You will need to add the unzipped file to a directory (either scripts or plugins ) that you must create yourself, then go to FILE/Configure/scripts and point to that directory. Make sure Preload Scripts is checked.
Some of these scripts will only work for 0.97 series so if you have 0.95 be prepared for it not to work!
Once you have done that re-start anim8or and you should find a new icon for triangulate mesh
If you intend using the orbiter spaceman ( I think thats what it is!) for animating I would check that the model is connected ( a lot of 3ds models are seperate objects) might be worth trying to use untriangulate mesh to change it to quads
hope that helps.
