The header is the rectangular area that runs across the top of your store containing your logo, navigation, search, and cart. It appears on every page to promote your company's brand and make it instantly recognizable to your visitors. This is a static section and cannot be repositioned.
Access the header through the theme editor
Go to Customize > Sections > Header to edit the header's appearance and features.
Enable sticky header
By selecting the Enable sticky header option, the header will remain fixed at the top of the desktop browser window while the customer scrolls down the page
Add a header logo
Your store’s logo provides branding for your site and a clickable link to return to the home page. By default, Reach will display your store name as your logo. To replace it, click the Select image button and locate the file to use. 200 x 100px .PNG image files work best for the Reach header, but larger images will be automatically resized to fit this constraint.
Use the Logo image max-height and Logo image max-width sliders to adjust the logo image's fit for the header.
Connect your navigation menu
In the Navigation admin, Online store > Navigation, there are two pre-populated menus: Main menu and Footer menu. Edit the links in these menus by clicking on the titles, or create additional menus by clicking the Add menu button.
Back in the theme editor, under Header > Navigation, connect the desired menu to your header. By default, it will display the Main menu. To change this, select Change.
Choose a navigation layout
There are two options for how the navigation is displayed for larger window and device widths: Expanded and Drawer.
Expanded (left side of the below screenshot) distributes the first-tier items along the header, while Drawer will collect all menu items into a collapsed menu link (right side of below screenshot).
If your header navigation has too many links to fit on one line, they will automatically collapse into a drawer, even if the Expanded style is chosen.