For one you can't download music from the computer to you iPod, that would be the other way around, You Upload music to your iPod,
In order to upload music to you iPod here are a few easy steps.
1. You can't use iPods like MP3 players e.g. drag and drop MP3 files into the drive.
2. In order to upload music to your iPod you will need to download iTunes on the Apple website.
3. When you have installed and opened iTunes the iPod will be recognized and put onto iTunes in the left sidebar.
4. Now all you need to do is put music onto iTunes and drag and drop the music in iTunes to the iPod column on the sidebar and it will sync and install the music.
Hope i have been of any help