I bought a microsoft zune 16 HD, and don't know how to put music on it?

I recently bought a zune 16 gb HD, and don't have any music on it. I have Napster, and have all my music files from napster saved on my computer saved in wma format, but I think Napster put a DRM or something on it so it can't go on my zune. Should I go for the zune p, or is there a way to get all the music saved on my computer on my zune? Thank you so much! Any comment is greatly appreciated!!