In most cases, the header or hero content in your website can be found in a header or hero content area. In Pages, you can find the page's content areas in the upper right corner.
View the content area that contains the hero or header image.
Your website likely has a Page Part specifically designed to be a page's hero image.
The current page's hero may be managed via Site Wide content, if that's the case, you will see a message when you view the content area.
Still having trouble finding the content are, use Visual Editor mode or enable Front End Editing.
If the page uses a Site Wide hero image, you can override that by installing the correct page part in the hero content area of the page.
If you're not able to figure out the right page part to use or you are still having trouble finding the content to edit, submit a ticket and we can help you!