Usually there'll be a usb cord that connects both the player and the computer. There may be a more techy way but I usually just open my computer so I can see the MP3 player like a thumb drive with files and then open my music and just copy and paste.
OR the other way that I found is that my laptop used Windows Media or whatever it was called and it had a bar for Sync music. I could drag whatever I wanted into that area and then hit the sync button and it would automatcally go to my MP3.
at 3:14 PM on Nov. 29, 2010