The mega menus are available only for top level navigations items only in “Main Menu” area.
(Please note that Mega Menu plugin is not included in Krypton theme)
To setup mega menu, first of all activate Mega Menu Element Panel from Screen Tab as shown in the screenshot by ticking three checkboxes :
Once The Panel is activated. You will see it on the left hand side
Any Parent menu can be set as Mega Menu by ticking Activate Mega Menu dropdown for this item checkbox, in example for contact menu below
The following image displays an example structure of Contact menu item with two columns dropdown menu :
Screenshot below shows expanded setting for mega menu column. You can enter any Bootstrap column width into CSS Classes
And screenshot below shows expanded setting for mega menu column