Assuming you're logged into our website, then look for the "Edit Profile" menu option. It's at the top-right, after you click on your profile image (or the placeholder for your profile image).
Here's the direct link: https://www.adoptabackpacker.com/edit-profile.
Scroll down to the "Photos" section, and click the "Edit" button.
You can then upload as many photos as your current subscription will allow. Easy!