How can I now restore my music which is on itunes back up discs

According to the support document you visited:

Restoring from a backup disc

1. Open iTunes.
2. Insert your backup disc.
3. iTunes will ask whether you want to restore from this disc. Click Restore.

I guess if this is a new computer we could add the following at the beginning:

0. Install iTunes.

I backup to hard drive myself so I've not had a reason to test out this aspect of iTunes.

tt2