#1 - Go to "Manage Pages" and then to "Content Pages"
#2 - Click on "Attach" for the Home page.
#3 - Paste & Link
Depending on where your video is hosted, go to the "Youtube Video" or "Vimeo Video" tab. Now you can copy-paste your link in the box, and click on the blue button to link the video.
#4 - Verify!
Verify the video preview frame is below the field! If not, check the URL first. If the URL is valid, make sure the Youtube video settings are set to allow embedding on 3rd party frames.