Fixture provides two convenient ways to add E-Commerce functionality to your website.  The first is to create a new Product page using the "Add Page" button under the "Content" section of the application.  This will produce a pre-styled product pages that includes payment buttons and the a beautiful way to display product images.  This works best with e-commerce themes that have a cart icon displayed prominently on the screen.

Payment buttons can also be added on any page the same way that you add other elements to the page in Fixture; using the green plus icon in the editor.  This method is used best for subscriptions and ad-hoc payments.