How to Load Music onto an iPod
Transferring your songs, playlists, videos, audiobooks, and podcasts to an Apple iPod (or other portable device) is as simple as connecting the device to your Mac through USB or FireWire, depending on the model. Each time you connect, the iPod automatically mirrors any changes to your songs and playlists in iTunes — that is, unless you select Manually Manage Music and Videos on the Summary tab in the iTunes window when the device is connected.
A connected iPod shows up in the iTunes source list under the Devices heading. Click the little Eject icon next to the name of your iPod in the source list before removing the device from a USB or FireWire cable.