The following information has come directly from the apple support web site.
Adding Content Automatically or Manually
There are two ways to add content to iPod nano: ? Automatic syncing: When you connect iPod nano to your computer, iPod nano is automatically updated to match the items in your iTunes library. You can sync all your songs, playlists, videos, and podcasts, or, if your entire iTunes library doesn’t fit on iPod nano, you can sync only selected items. You can sync iPod nano automatically with only one computer at a time. ? Manually managing iPod nano: When you connect iPod nano, you can drag items individually to iPod nano and delete them individually from iPod nano. You can add songs from more than one computer without erasing songs from iPod nano. When you manage music yourself, you must always eject iPod nano from iTunes before you disconnect it.
The following URL will bring you to the iPod Nano manual. For more information on setting up you iPod see chapter 2: Setting up iPod Nanohttp://manuals.info.apple.com/en_US/iPod_nano_5th_gen_UserGuide.pdf
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