There are 3 menu locations in the theme, to help users navigate your site, the Top Header Menu, The Primary Menu and the Secondary Menu.
How to set up Multi-Column Drop-Down Menus
Edit your menu and add
mega-menu in the CSS Classes box, as you can see in this screenshot:
If you cannot see the CSS Classes box, click the “Screen Options” button at the top of the screen and make sure it’s enabled.
Then start organizing your multi-level navigation menu: