Need help - how to get itunes to scan for music?

Please help, I just made a mistake. I was moving my itunes folder to a public account so that I can access it from any account. Then I decided it was going to take too long, so I cancelled it.

When I opened itunes back up it said scan for music, and I did, but accidentally cancelled that too. So now I only have a fraction of my music there.

Please tell me how to get itunes to scan your hard drive for your music files?

I have no back up folders and I'm really nervous that I just lost everything I had.