First, click on the "cart" icon in the upper-right corner of your computer screen. This will allow you to view all items currently in your cart as well the quantities that you have chosen for each item. To change the quantity of an item in your cart, move your cursor to the "quantity" field for this item and type in the quantity desired. Once you do this, the quantity  and associated dollar amount 'if applicable' will be automatically updated and reflect the correct amount for both quantity and cost located on the right side of your screen.