This article explains how to add a featured image to a web page, in the space highlighted below.
1. Go the page you would like to edit, and click edit page in the upper bar
2. Once the editing page screen loads, find the "Set Featured Image" option on the right hand side.
3. Before clicking "Set Featured Image" note the recommended size for the featured image.
When you click "Set Featured Image" you will be taken to media library to upload/select an image. Once an image is selected, it will display in the featured image field.
4. Scroll to the top of the page and click "Update"
5. Click "View Page"
The selected featured image will now display at the top of the web page, behind the page title.