Unlike banking points, which must be done before making a reservation that uses them, borrowing can occur only at the time you make (or modify) a reservation. The online reservation system will show a borrowing option on the page where you choose contracts to apply to the reservation if contracts chosen to apply do not have enough points to complete the reservation without borrowing. You cannot really screw up the process because, if you actually need to borrow points for the desired reservation, you won't be able to get past that applicable page until you have selected to borrow points.