Install Google Tag Manager
Set up variables and triggers for video
Finalize tag
Need to set up: Tag Configuration and Triggering elements
click the “Tag Configuration†option
Select “Track Type"
Select "Event"
Set the parameter for Catagory, Action, and Label
Set Google Analytics.
Go to admin-> click property -> Click Custom Metric -> select Custom dimension -> Add custom metric
Select overview -> Check Events
For more details on Google Tag Manager,
refer Beginners Guide on Google Tag Manager: