I always go to Google Support for the most up-to-date information on Google products. In the case of Hangouts on Air, this would be Get Started with Hangouts on Air in the Google+ Help Center.
But where exactly where are the Hangout-on-Air Controls?
It took me a while to figure out where everything is located, so I thought I'd share my findings, to save you some time.
I introduced this presentation on our Google Rocks! Hawaii HOA. Check out the discussion:
Have fun hanging out!