Create usable ISO back up.

My daughter has just ruined her second copy [physical disc] of the Sims3. I had to go buy it again. Last time I created an copy of the disc thinking I could use that b/u and save the original. I was wrong.

Today I then read that if I used Daemon tools I could.
So I installed Daemon Tools Lite.
But I can still not get it to work.

Was I misinformed?
If not what and how do I use it?
Is there a tutorial somewhere?

Thanks for your help
-Eds