Q: my Ipod classic is full. i want to start another itunes library to use with another ipod. how do i do it

Here's how to create a new iTunes library

Open a different iTunes Library file or create a new one - Apple Support

But instead of creating a new iTunes library and switching between libraries (which is less convenient) just to sync two different iPods, you should use one iTunes library, and sync different content to each iPod.  You can still do this automatically, with minimal manual work.  For example, if you have audiobooks or podcasts synced to your iPod classic now, leave that content off the current iPod and sync them to the other iPod.

You can create smart playlists by genre and sync certain genres to one iPod and everything else to the other iPod.  You can post back for tips on creating smart playlists to do this and many other things automatically.

If you have a lot of playlists that you've created over the years, you can set up syncing for certain playlists (a different set) for each iPod.  There will be some songs on both iPods, but using playlists may be the most functional way.