If you would like to add a video to your main page what you need to do is click on the Integrations tab on your Dashboard.
Find the Youtube intgetration.
Add the Video ID of the video you would like to add.
Now this video will appear at the top of your primary BLAB page. Many Bosses use this space to have an introductory video (who are you and what are you all about type of thing) but you can add any type of video you prefer.