Here are the steps on how to use Promo Code when shopping at castr.com: You can view your existing Castr Promo Code by logging into your account, viewing your profile and clicking [My Card]. If the product you want to buy complies with the Promo Code rules of use, then you can add the product to your cart. Then, click Pay, select the corresponding available Coupon Code, and select your preferred payment method. Please note that each Castr Coupon has its own rules of use, if your order is eligible for castr.com, it can be used.