I have not understand how to create displacement maps , the "big feature"  since iClone 6 .

I have even buy a tutoria,l but not working  for me That Tut is more confusing  than helfull 

What is the secret of this feature ? How can I create such a map in Zbrush  for iClone in easy steps? 
I think why it is not so popular, because  nowbody know how to make.this 
Maybe someone can change this ? 

I would realy know how it works