...I know it! I KNOW IT!!! (jaja... ) Have you tried to select de Add Bone tool in the Bone tools section (that with the + simbol under a bone draw) and click and drag in the editing window?? ENJOY!!!
Also, are you reading the tutorials? Select Help from Moho's Help menu to bring up the manual, then follow the links to the Tutorials section. The first few tutorials will walk you through the basic steps of drawing, creating bones, and animating.