Videos should be added as the first line of the product long description. Product long description will need to be sent as html.
It should look something like below:
<iframe width="560" height="315" src="https://www.youtube.com/embed/lSWOgTwUMWY" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>
When you go to youtube/dropbox/google drive videos, there is a embed option, which gives the embed HTML.