If you are talking about a new model you made, that appears to be a very difficult and more than anything, annoying task. I found a tutorial for it here: http://merlin.zsnes.com/tutorials/mapping/index.html (btw, check out some of the models that guy does, they're amazing) heres another one, this one you have to download a MAxscript for GMAX called chiliskinner: http://www.chilliweb.co.uk/chilliskinner/
(it works in GMAX, I tried it) basically, you lay out all your stuff flat or something like that, didnt really get it myself but I am a newb when it comes to 3d modeling.
hope that helps.