We do not have a flow chart that indicates the cart's functionality. The process goes like this:
look at the products results and click on the learn more to go to the detail page. From here you can choose your options and add the item to the cart.
Once you add the item to the cart you will be taken to the cart page to see your items. On this page you can update the quantity of an item, delete it from the cart, continue shopping, or checkout. I know this is not exactly what you are looking for but I think this should be enough for you to list some steps on the page.
To get a better feel for the functionality you can check out the Power Store demo here: