Put the "Cart View" stack anywhere on the page you want to be able to view the cart.
You'll need to add the Cart Enabler stack on any page you want to add a View Cart, Cart Simple or Cart Variable button.
This enables the cart to pop up, otherwise it will just redirect users to the PayPal page without a pop-up.
There is also a "Cart Return" stack. Add this to any page where you want the cart to automatically clear
after been redirected back to your site from PayPal.
With the buttons you have to add a "success" page for a successful checkout. It's optional but in some cases
after returning to your ecommerce store you may want the user's basket to be empty again.
In that case, you would use this stack. Otherwise, no need to apply it.