Diamond mp3 model dsm941. How do you get music on this @#$@%^ thing? I bought this for my son and

Question

How do you get music on this @#$@%^ thing? I bought this for my son and I can't seem to download any music to it! Please help me, I have only been able to put one song on it for him, although when I go to the delete section, all the stuff I put on it seems to be there. The instuction book that came with it tells me nothing.