The recommended size for a header image is 675 pixels wide by 315 pixels tall.
Click "edit" on the page you want to add a header image to. Once on the edit screen, click the "Layout" tab.
On the layout tab, click "Header Content."
Choose the "Photo Feature: Single photo at top" radio button.
Add the image by clicking the "Select media" button.
A pop up will appear and you will be taken through the standard three screen image upload process. On the second screen is where you will be able to add a caption, credit and tag to your image, however, we do not recommend adding a caption to a header image.
Click "Save Draft" or "Publish" to commit your changes, and view your page.
Editing your Caption and Credit
If you would like to update your caption or credit just come back to the screen above and click on the "Edit Media" button.