Using your account credit to make purchases.
To use your account credit, just be sure to check the box at checkout that says "Click here to use account credit." You will see your order total adjusted on the next page before you actually complete your order.
Please note that you will still have to select another payment method if there are not enough funds in your Gift Certificate Account to cover the cost of your purchase. If you have more funds in your Gift Certificate Account than the total cost of your purchase the difference will be left in you Gift Certificate Account for the future.