You can update the quantity- just enter the desired quantity in the 'QTY' box and select 'Update Quantities'. If the requested quantity exceeds the available stock, your quantity will be adjusted accordingly.
You can add more items to the shopping cart if you select the 'Continue Shopping' link
Once you are ready to pay- select the 'Check out' tab. If you are not logged in, you will be directed to the log in page.
How to register with Multicart Shopping Cart