I have little to add to the very thorough post by Acadia except to say that the electronic reference manual that comes with Poser 6 does give a (brief) step-by-step account of prop-based hair and conforming clothing starting on page 198.  I assume the manual is basically the same for other versions of Poser.

If you're finding yourself getting stuck quite often, there are also some useful books available to help you learn the program.  Practical Poser and Poser Revealed are two of the most popular, though I'm sure there are others.  I'm still learning the program too, and I'm sure that I've saved myself hours of frustration by having the latter one handy.