In order to edit the Header, go to the Homepage and hover with your mouse on the Header. Click on it and you will see a popup to Open Global content editor. Click to open the Global content editor where you will be able to edit the following settings:

Logo:
Upload the logo, define the dimensions of it and the alternative text.

Menu and Socials:
Select the Main Menu and the socials for your header.

Language Switcher:
Enable/disable language switching in the Uranus header.

Header Button:
Insert a header button that you can configure differently from the main menu.

You can discover more about the Global Content and learn how to edit this on this related article.