To get a cart functioning with a page, here are some basic steps to take:
1) Create an eCart Object.
2) Run through the Display Manager.
3) Run through the Checkout Wizard.
Creating the eCart Object will not add anything to the page. It just creates the object that will be used in the later steps of creating your cart. When running through the Display Manager and Checkout Wizard, you will need to specify the eCart Object that you created earlier. After running through these steps, you can apply some add to cart buttons to the pages where you want to add items to the cart.
Could you clarify what part of the process you are on when you are running into this issue?