Update README.md

Author: AmyyD

README.md

@@ -48,6 +48,8 @@ Go to `Admin Panel > Stores > Settings > Configuration > Magepow > Categories`
 
 #### In categories page
  ![config-module-img](https://github.com/magepow/magento2-categories/blob/master/media/frontend_category.png)
+ 
+### How does Magepow_SubCategories work? (https://www.youtube.com/watch?v=k3A7PBh-NbQ&lc=UgzCFSLUqlD6cl__PH54AaABAg)
 
 ## Donation