Within the header of your Testament theme there are several options that help you to setup your content easily and from one easy to follow section which will be accessible on every page within your themes editor.
In your Shopify admin open: Themes > customize theme
On the left side of the page click on the Header section to reveal the following options:
Logo - add your own custom logo image or alternatively if you do not have a logo as yet you can show just the name of your store plus configure it's text size, weight and case.
Promotional text - by adding text to this section you can alert your customers of any promotions, notices or simply welcome them to your store. Leaving this field blank will remove that message.
Cart icon - switch between a Cart or bag icon. Note that the terminology across your store will require changing should you wish to use Bag... Editing the language of your theme via the Online store > themes > menu will give you access to the language editor.
Navigation - choose a main menu for your store and configure it's layout options which include a mobile only style for those who require a minimal look to their store.
Mega Dropdown - the theme features a sticky navigation which will help your customers to find their way around your store regardless of what page they are on or where they have scrolled down to. Within this navigation you can also add a mega menu to one of the links in your main menu. This mega menu can show 4 menus from one single drop down, all that you need to do is enter the name of the link in your main menu that you want it to drop down from and then choose menus that are to show when this is hovered.
At the bottom of this section you will use the Content section to add menus to this mega dropdown.
A store has the following links in their main menu:
Home | Shop | Blog | About us
Shop is entered within the Mega drop down link title field.
Under the Content section at the bottom of the menu 3 out of a possible 4 menus have been chosen
When the Shop link will now show a mega menu containing those 3 menus.