Hi everyone! I am new here to the forum and fairly new to zbrush. I was using zbrush 2 for a while and it was very easy to subdivide a zsphere structure (after finishing zsphere model press shift D and it would subdivide) But now that I moved to Zbrush3.5 I cannot for the life of me find a way to subdivide the mesh. After I create the zshere skeleton and sketching the muscles ontop, I press ‘A’ to preview the mesh but i dont know what to do after that? If anyone could help me that would be great 
Watch the Sketching with ZSpheres video tutorials in the ZClassroom (link at top of the forum). This explains what you need to do.
Richard