Menu items will have no Mega Menu parameters if it is the first time you are enabling Mega Menu. Therefore it will look similar to a regular Moo Menu:
In the image given above, you can see the Features menu item showing four child menu items:
- Module Positions,
- Module Variations,
- Error Page
You have to edit each items to make it appear along with its child item; thus the contents of parent and child menu items will show up. You have to click the Features menu item to do it.
As the image given above shows- just selecting Yes for the Group option will group the Features menu item with its child menu items into a compact column to link with the parent menu item Features option appears at the top of the first column of the main menu item Joomla! Stuff.
Now you can do the same thing for the other two parent menu items,i.e. Menu Menu Showcase and Custom HTML.