You can edit your Shopping Cart by clicking on the Shopping Cart symbol on the right side of your screen or by clicking the link "To Shopping Cart".
Within the shopping cart you will be able to change the quantity of each contained product or delete products from your shopping list:
To delete a product check the delete box in the product row and click "Update". The product will be deleted from your list. To change the quantity of a product simply change the value for the selected product and press Update to save the change.