Take a look at
ebruere's tutorial on MTS2.
Dizzy had a similar tutorial, in fact he had a lot of great tutorials over at VariouSimmers, but that site seems to be totally dead now. It's a shame too. I would have liked to have kept those tuts as a reference. Maybe Dizzy might be kind enough and repost them here in the Bowels of Trogdor?
Here is a link to
ebruere's "Let's Undress" example mod. FYI: It was originally on MTS2, but it has been moved to their
adult affiliate, Sexy Sims 2.
If you are totally lost, then I would start with reading some of the more basic tuts over at MTS2. Echo and AdidasSG2 have several great tutorials, for both elementary and "advanced" levels.
Ste