To add a video in a newsletter, follow these steps:

1. Open the Broadcast Message editor 
2. From the Content section, drag the video widget to your desired newsletter location.
3. Click on the added video widget to display its content properties.
4. Insert the video's URL (only YouTube and Vimeo links are supported) into the provided URL box.
5. Click "Save" to incorporate the video into your newsletter.

Make sure the video is publicly accessible for all users to view!