1. Install the YouTube App from the App Store.
  2. From within MeeZee Workouts, click the Work Out button.
  3. When the page with your workout loads, click the "Screen Cast" text in the middle of the screen.
  4. From within the YouTube app, click the button at the top of the video that looks like a square with wireless signals coming from the button’s left corner.
  5. Choose your smart TV.

For details of using the YouTube app please visit this page from YouTube:  https://support.google.com/chromecast/answer/2995235?hl=en