This page explains about - "How to add video to Detailed Pages" (at the beginning of the Detailed Page)
Note that 'video' in Detailed Pages is supported only in a two Detailed Pages Designs. (Goto 'Detailed Pages' sheet and look for 'Design' column in Column F). Thought the below names say 'Images' - videos are supported as well.
Image top & Text bottom
Image left & Text right around
Image right & Text left around
If you want to try video in Detailed Pages design, just add Video link (Youtube link or mp4 link or webm link) in 'Detailed Pages' sheet -> Design Column (Column F) for the required rows.. Otherwise you can just use images also simply.
Below video formats are supported.
Note that 'video' in DetailedPages is supported only in a few Designs as mentioned above.
Goto 'Detailed Pages' sheet and change the dropdown value in 'Design' column (Column F) for the required rows to try this feature.