OK. First you need to load the transmap into the transparancy channel. Then you need to play with the transparancy sliders. I don't have Poser reinstalled on this machine (the curse of upgrading), so I can't give you the exact settings for certain, but IIRC, you need to set the minimum transparancy to at least 50% and maximum to 100, and the falloff value very low, but you may need to tweak these in order to get the desired level of transparency in the render. Now it depends on your display settings as to what you'll see - but when you render, you will see segments of the model become transparent regardless. It's covered in the manual, but not particularly well (this is one of the more confusing sections, IIRC).