Just Got My Greyhound! What Is The Next Step To Becoming A Therapy Dog?

I just adopted my wonderful greyhound yesterday!, and I am really interested in training him to be a certified therapy dog. Where would I start, and what are the steps? I know that I would need to get the CGC certification, but how do I get into that? I also know they have classes for it, but are those classes required? Or can I just personally teach him what he needs to know and have him take the test?
And after the CGC test, what is the next step to becoming certified for therapy? Are there different kinds of therapy certification based on what kind of therapy work you want to do? I would really like to take him into hospitals.
Any advice would be greatly appreciated!