From your store's Dashboard click the Site Designer icon in the left Navigation Menu.
Your store offers a default Header Block as well as several different header options. These optional Headers can be accessed by adding them to your store's Homepage. Make sure the dropdown menu at the top of the Site Designer page is set to Page: Home. This will ensure that your new header applies to all of the pages on your store.
On the Home Page, mouse over the page until you see the Plus Sign icon to add a new block. Click the Plus Sign icon and locate the Header section of the Add A Block menu. Open the section and choose Simple Header, using the Add Block button.
Once your block has been added, hover over the new header section and locate the gray Edit button. Use the Edit button to open the Edit Block menu and customize it.
The Edit Block menu for the Simple Header offers these options:
Header Block Controls
Trash Can Icon to Delete Block
Arrows to move block up or down the page
Make This Block Reusable Toggle
Background Color Chooser
Text Color Chooser
Hover Color Chooser
Border Color Chooser
Make sure to click the Done button at the bottom of the block edit section to save your changes.
Additionally, you will need to click the green Publish button at the top of the page to make your changes live on your store.
You will likely want to remove the default header at this point. To do so, locate the default header, easily distinguished by its green Edit Template button, visible when you mouse over it. On the right side of the default header, you can click the Trash Can icon to delete the default header.
As a final step, make sure you click the green Publish button located at the top of the page to make your changes visible on your customer-facing site.