You likely reuse images across your website on multiple pages. You don't need to edit each page if you need to update a banner, logo, or any image. Instead, you can replace the image in its library, and the system will automatically replace it across your website.
Find the image you want to update in your Photo Library or Web Graphics library. You can generally search by file name and title.
Click the Edit (pencil) icon. In the pop-up window, choose the new image from your device and click Save.
Images you replace will update automatically, though you may need to clear your browser cache to see them.