Chromecasting from mobile devices is NOT supported.
To cast the webcast from your computer's Chrome browser to your Chromecast device follow these steps:
1. Click Cast on the browser options.
2. In the pop-up casting menu click the 'Sources' dropdown menu and select 'Cast Tab'
3. Select your Chromecast device.
You can click the "Full-screen" icon on the video player to expand the video.