Easy! Once you proceed to checkout, on the right hand side of the screen, you will see a detail view of your cart and the breakdown of your price. Between the items in your cart and the price breakdown, you have an option to apply a promo code.
Click on 'Apply a promo code', enter your coupon code in the given box, and click apply! Once done successfully, you'll receive a confirmation message and your order total will be updated in the price breakdown below.
If you have any troubles, please don't hesitate to contact us! Call (888) 316 - 7297, Text (833) 316 - 1577 or click the Chat Now button. You're also welcome to email us at Help@PetFlow.com.