Just go straight to your About page. At the top of the page is a thin blue strip that says "Shop Tools" and one of the options is "Edit about page". Once you're in the editor you should be able to upload photos.
Alternately, you can go to your Dashboard. Click 'Settings'. Then along the left-hand side of the screen, scroll down to 'Shop Setting' and click on 'About'. When you're on that page, choose the tab at the top of the page that says 'Story'. Then you can add photos, it's towards the bottom of the page.
Hope this helps!
