1. Find the product you want to edit from the product list. When you open the product, you can see the video(s) there are for that product.
2. Click OFF from the ON/OFF switch shown on top of the video you wish to disable.
That's it, the video you disabled won't be shown for this product any more! You may just need to refresh the page. If you would like to put it back later, simple choose ON from the switch.