When you're viewing a Page, the Header section contains a Title and Description. In some Themes, this information also appears overlaid or below the Project Cover when you're in a Gallery.
The Header section content can be edited by:
A) Clicking the blue pencil icon on the top left corner and then selecting "Edit Page Info".
B) Clicking "Edit Page Info" in the Remote under the "This Page" section
Either of these methods will open this box:
To edit the margins, alignment, or font, you can:
A) Click the blue pencil icon on the top left corner and then select "Customize"
b) Click "Page Header" in the Remote under the "This Page Section"
Either option will open this menu where you can edit the look and feel of the Header section: