How do I change the thumbnail for my Demo Reel?

How do I change the thumbnail for my Demo Reel? I have logged into account on IMDB Pro, selected 'edit videos', selected my demo reel, and the only option is "Allow IMDb to update which video displays at the top of your IMDb page" (or to choose yourself). There is no mention of thumbnails. Can we add a thumbnail like you can on YouTube? Thanks.