We've designed Envato Sites with the goal of making it easy to create simple, functional websites. With that in mind, we've steered clear of building features like shopfronts and shopping carts, instead focussing on making it easy to work with a few popular external e-commerce systems.
Check out our guide to creating a Products or Services section on your website.
If you would like to sell products or services on your website and you do not wish to use one of the solutions mentioned above, you can choose an alternative e-commerce system. Here's our guide to choosing a solution that works for you. Once you've set-up your store and added products/services, you'll be able to link customers from your website to your online store. See our guide to creating buttons and writing product descriptions here.