There are two parts to this, first you will need to add the user to the website they need to edit, and then you will need to make them the author of their profile page.
These directions will show how to swap the image of a hero banner. There is more information about Hero banners on the Sitefarm website at https://sitefarm.ucdavis.edu/training/all/hero-banner . You will also need Site Manager access to the website you are editing to make these changes. If you need Site Manager access contact lshelp@ucdavis.edu.