There are two ways to add a promo code. The process is the same for Fave deals and FavePay:
Method 1: Click on the ME tab > Tap on ADD PROMO CODE > Enter the promo code and click APPLY > The promo code will be automatically applied to your next purchase.
Method 2: At the payment confirmation page, click on HAVE A PROMO CODE? > Enter the promo code and click APPLY > The promo code will be applied and you may complete the payment process.
You are also able to change or remove the current promo code to another one of your choice. Just simply click on Change or Remove in the Promo Code section.