Shopify's menu builder
In the Shopify Dashboard, go to Online store > Navigation. There are two pre-populated menus: Main menu and Footer menu. You can edit the links in these menus by clicking on the titles to edit them, or create additional menus by clicking the indigo Add menu button.
Note that mega menus are only compatible with Startup when the menu style is set to Below header. They will be automatically triggered when each second-tier menu item has at least one third-tier menu item.
Connect menus to the header in the theme editor
By default, it will display the Main menu. Choose another menu to display here by clicking Select menu.
Change the navigation layout
You can customize how you want your store's menu to display using the Menu style dropdown below. Startup's header navigation has three positions: Header, Below header, and Drawer (meaning the menu is hidden under a mobile-style "hamburger" icon until activated). Note that even if the menu style is set to Header, navigation will collapse into the 'Drawer' if there is not enough screen space for the menu items to fit.