Many people haven't yet figured out the new default interface in iTunes 11. To get to the iPod information so you can sync, click the iPod button in the header bar at the upper-right, e.g.:

Or go to the View menu and select "Show Sidebar" and the interface will then look substantially like it did in earlier versions. If you don't see the menus, press Control-B or go to the small icon with the arrow at the extreme upper left and select "Show Menu Bar":

If your nano still doesn't appear, the troubleshooting assistant may help:
http://www.apple.com/support/ipod/five_rs/
Regards.