Click the βTextβ button in the Top Bar
Upload an image OR Select a free stock image
Click anywhere on the canvas OR click and drag
Set crop an focus settings in the Style Panel
Select a section
Click the image background icon in the Styles Panel
Select an image as before
Now you have an image as a background
There are dedicate elements/sections that go beyond static images, such as slideshow, image compare, and scrollytelling. See the dedicated reference pages for more details.