Start by going to the Store tab and selecting the Products section; you'll find an Add Product button here.
From here you can add a title and description, as well as enter a price. To add photos, simply drag them into the Product Images box or click the Upload Image button, and select images from your computer. There are no set limits on the number of images you can upload for an individual product. If you add more than one image, the images will show up as a clickable slideshow for your customers.