Hover over the area encircled here until you see four dots
Click on the four dots
Click on "Edit"
Click here to expand the "Advanced Settings" section
Click this checkbox to "Enable video as default for slide show mode" option
Click on "Update"
Click on "Publish"
The guide has been published, click on "OK"
The settings have been updated after publishing!
You need to wait till the Video is being processed. You can view it under download options, once it is available
When you click on "ShowMe" button, it will automatically start playing the video of the guide in ShowMe mode subject to its processed