Hello,
All I used was ‘wp-video-lightbox’ in the ‘link relationship (XFN)’ field in the menus section to make that video pop-up the way it does.
I downloaded the plugin, customized how I wanted it in settings and then went to menus section and added the ‘wp-video-lightbox in link relationship for it to be responsive with the ‘Play Video’ menu button.
I added no other code or anything besides this.