You now have several options to share a video in a meeting/event.
If you actually have the video file on your PC, you can share it in a meeting by clicking on Share File (Including video) in your Webex meeting. This will pull your video into the Webex meeting. It is not recommended to share files in a meeting like this that are over 20MB. When you click play on the video, it will play on each participants machine and they will hear the audio for the video through their speakers or headset.
For web based videos, you will want to choose Share Multimedia in Webex. This will bring up a box asking for a URL. You must place the exact URL leading to the video into this field as you will not be able to look for the video once you enter the URL. For example, if your video is on You Tube, you must go to You Tube ahead of time and copy the URL at the top of the page once you have your video up on the screen. That is the URL you would use in the Webex multimedia window.
All other methods of sharing a video in a meeting (Screen Share, Application Share, Web Browser Share) will result in the video being seen by the audience but the audio will only play on the host's computer. This means the host would need to hold their phone up to their speaker in order for the attendees to be able to hear anything.