Hello, Ash,
Thank you for contacting us and for using XStore.
To add videos to the media carousel element, you must upload the video to your site under the media section. Once the video is uploaded, it will be available for use.
We regret to inform you that it is not possible to use YouTube links in the Media Carousel element. If you would like to add this functionality, please contact our development team by submitting a feature request at https://www.8theme.com/taskboard/
Kind Regards,
8theme team