how do yo use i tunes to sync music?

Answer 1

Easy. You buy (download) songs off of iTunes. Then, when you plug your iPod into the computer, to the left there will be a small iPod with your name next to it. Click on it. Then, at the bottom of that page, you will see a button that says "Sync". Simple.

You can also import songs from CDs, etc. But it's the same way to sync.

Answer 2

you will need to use a utility to pull the files off your iPod onto your HD, then add them to your iTunes library from within iTunes interface. THEN sync your pod... Podworks is cheap and great.
Podworks: http://www.versiontracker.com/dyn/moreinfo/macosx/17443