What is a Hero Photo?
...
Hero photos must be carefully composed and cropped to work well on both desktop and mobile devices.
A Hero Photo must be at least 1600 pixels wide by 900 pixels tall. To ensure flexibility in cropping, we recommend that the source photo be 2000-2500 pixels wide.
The middle 1/3 of a hero photo must contain the relevant action and be the focus of the photo subject.
Anything outside of that middle 1/3rd will be cut off when the web page is displayed on smaller screens. See examples, below.
...
Edit the page by clicking the Edit button.
Click on the Hero Photo section, above the Title.
Click Choose File link to select a new Hero Photo image from your computer.
A file browser dialog window appears.Browse your computer for an image, click Open, then click Select.
Complete the Alternative text field, then click on the image once to apply the cropping.
The "Cropping Applied" message will appear.Save the page.