Step 1: Create the relevant menu(s) in your Shopify Navigation settings. You will need to create your primary menu as well any additional sub-menus.
Step 2: While planning out your shop, give some thought to which primary menu items will require the Mega Menu treatment. In our example, we want to create a mega menu under the "Earrings" link in our main menu:
Step 3: Go to Admin > Online Store > Themes > Customize > Theme Settings > Mega Menus (1) and then Check the boxes next to as many mega menus as you will require (2).
(1)
The first step will be to enter the link title for each of your new Mega Menus. For our example the title needs to be "Earrings" as that is the title in the main menu.
Step 5: Click the "Add Column" button to add up to 5 columns to your menu
The layout of the column contents can be found below: