You need to download the latest version of iTunes from Apple (the "itunes store" is not involved).
http://www.apple.com/itunes/
The disc that came with the iPod will have an older version of the software, so download the latest. Install iTunes. Put all of your music and other media into the iTunes library. Connect the iPod. It should be recognized by iTunes. Depending on the current settings on the iPod, it may or may not ask if you want to sync the iPod to the iTunes library. If you sync, the music in your iTunes library will be copied to the iPod, and replace whatever music is already on the iPod.
If you want to
Restore the iPod to erase it and and initialize the software, select the iPod in the iTunes sidebar and click on the
Restore button. This will install the latest available software for the iPod (technically not "factory settings"). After the
Restore process completes and the iPod restarts, iTunes will again ask if you want to sync the iPod to your library or not (do it manually).
