Can't figure out co-hosts in webinar

We recently upgraded our account for a month so we can run a webinar. I need to have 2 co-hosts in my event. I watched the 'how to' video and did the following:
- made sure that the co-hosts toggle was 'on' in settings -> meetings (basic)  (It was already on when I looked)
- ran a test webinar where I tried to make a panelist a co-host but that option did not appear
- I also tried to make a regular attendee a co-host and had the same problem.

I see lots of other options - like making a regular attendee a panelist, but I don't see any way to make someone a co-host. 
Help?