Changing page images
Page images appear at the top of each page and in the explore section.
Editing the image
Go to page
Find the page you want to edit.
Edit the page
Hit the cog in the top right and select 'edit page'.
Across the top are a number of options, select 'Metadata'.
In the 'image' section at the top, upload an image and add a description.
Scroll to the bottom and hit save.