I have created a number of points with pictures using Story Map Tour, but the button ESRI refers to, and even shows a picture of, is not available.
Here is the blog post I found where they suggest the button to press... https://blogs.esri.com/esri/arcgis/2015/08/12/add-youtube-videos-story-map-tour/#comment-9716
But, this is what I see when I follow the steps...
I simply don't have the option of choosing video after clicking the "add" button.
Please let me know if you know where to find this button in the Tour version of Story Map.