At checkout, you can redeem your reward points. If you have accumulated enough points to redeem them, you will see the option to use points on the checkout page along with the payment methods.
The option to use the reward points, as well as your balance and the monetary equivalent of this balance, will be shown to you on the checkout page. The redeemable reward points can be used in conjunction with other payment methods. You need to accumulate at least 5000 points in order to use the reward points.