In the Header and Footer subsections of the Navigation tab you can update the available options for each site menu. Click on the navigation menu you would like to update.

The menu structure will contain all enabled pages on your website. Use the two lines icon to reorganize the pages in the header navigation. If you would like to create a submenu, use the two lines to drag the page and drop it slight indented to the main page.

To hide a page from the navigation, click on the 3-dot icon and click "Hide from menu".

You are also able to create a Mega Menu from this menu. To learn more, visit the Mega Menu knowledgebase article.