Each product is displayed on a generated product page. You can add other elements onto this page to create a long description for your product. To do this, in the editor, click on the product as it appears on a category page, in a product element, or from the Edit Product page. This brings up the product page in the editor and you can change it as needed.
Note: To see the Go to product page link on the Edit Product page, you first need to save a product, then go back and edit it.