Once you've uploaded it as a Material, any Event Admin who has Presenter controls (Hosts/Presenters) can share it during the webinar.
Sharing a Video
From your event room, you'll want to access the Sharing Options menu located in the bottom-center of your screen.
From there, you'll find a list of all the different items you can share including any Video Materials you may have added.
Simply select the video from the list, and it'll start sharing with your audience immediately!
To stop sharing the video, you can navigate back to the Sharing Options menu and select Stop Sharing Video.
Or you can quickly over to the bottom-centre of your screen and the red pause icon will appear to Stop sharing this video.