Video Call - Hangout on Google+ with limited to 10 participants

I tried to join the video call on Google+ event today but got it's full all the time.

Hangouts video calls are limited to 10 video conference participants, with no time limit. You can also use Hangouts On Air to broadcast a Hangout to many more people, though there is still a limit of 10 active participants. [FAQ]

 So the key point here is people need to broadcast the hangout via Hangout On Air but I don't find it or not sure if I were understanding it well.

I will try to understand this feature more and share again.