How to enable video option for the attendees in the webinar?

https://support.zoom.us/hc/en-us/articles/115005474943-Meetings-and-webinars-comparison 

Look at the section called Video Sharing

Hi @LodhaCo , Zoom webinar is for attendees to listen and view only. There is no option for them to turn on their camera. The only way to do this is to promote your attendees to panelists in the webinar. Otherwise, I'd recommend scheduling a Zoom meeting so that all attendees have the ability to turn their camera on. Note that Zoom meetings have a capacity limit depending on your license. The biggest Zoom meeting license is 1000.