HM =
Holdem Manager ... I don't see the point in having Holdem Manager, as it is nearly the same as PT, only it is still in beta. It looks more promising than PT, and right now it is also free. So I'm using HM right now. If you already have PT, don't bother yet.
As for how to use PT,
this thread contains a great analysis of what your stats mean and what you should be looking at in PT