This is the page you need to edit in order to alter the photos at the top of each page. To add new images, click on the “Add Media” button underneath the page title. Please ensure all images are 680px × 450px. Even if you upload correctly sized images, by default WordPress will resize them. To prevent this, please ensure the “size” option is set to “Full size” on the right hand side of the Add Media screen.
If you have any difficulties please let me know.