Just bought IPOD NANO..how do i get music already downloaded on BearShare onto my IPOD?

I just bought a 4gb Ipod Nano...and i already have music downloaded on BearShare...how do i go about getting it on my IPOD..i tried dragging it onto my ITUNES but it said it would only accept a few of the songs because they were in WAV format(or werent..one of the other, i cant remember). I also already have a few songs in ITUNES...how do i get them on the IPOD.