How to prepare a webinar?

Hi Team Brooke,
I was asked (out of the blue!) to do a webinar for a person’s community. I love her content and think it would be like guest blogging and could give me some visibility in front of new group pf potential clients. It would be also great, as I admire this person and she does something different than me (nutrition), but related enough (I’m all about mindset, the model etc). Plus one of my goals this year has been to get a much bigger audience. So this might be a good step to take. BUT: Although I have A LOT of teaching experience, I never did a webinar and I have no idea how to create content for that format. I mean – how to choose topics (how many, already?) for something like a 20Min teaching? I normally do 2 day workshops or so… Any hints/literature/tips? Thank you!!!