Header settings are located in Appearance → Customise → Header Settings.
Activating the Make the navigation bar sticky option will make navigation bar visible when scrolling.
By activating the Enable the smart sticky feature navigation bar will be revealed when scrolling up and hidden when scrolling down. The feature allows you to save viewport space when viewing your website.
Header Top and Main height
You may change the height of the Header Main for desktop and mobile versions. You may also adjust the height of the Header Top.