Once shopping spree funds are added to your account, you can start a shopping spree order from your iOffice.
Click on the toolbox icon and then click Place an Order. Select Shopping Spree as your order type.
You will select product as normal. When you get to the payment screen, there will be an option to pay with your spree funds. You will update the price for amount you want to use. If you have an overage, you can add a 2nd payment for charges to your credit card.
Reminder, shopping spree funds expire one year from the time they are assigned to your account unless otherwise stated when added to your account.