You will be given the option to redeem your Reward Points on both Subscription and non-Subscription orders during the check out process or in your Subscription Dashboard (Click Manage Subscriptions after logging in). Your options will be available on the right hand side in your cart. You can apply a reward that you already have or redeem points for a new reward. The code can then be copied right into the discount code section. Please note, you can only apply one reward per order/Subscription.
You may also choose to redeem your Reward Points from inside your account. Just click Loyalty Rewards to redeem your points and view all available rewards you have already redeemed.
If you are trying to apply your Reward Points to an active Subscription, the process is slightly different. View all info on this process by visiting this article: How do I apply Reward Points to a Subscribe & Save order?