Here's how to use Promo Codes when shopping at Factory Mopar Parts: Sign in to Factory Mopar Parts or create a new account to add your favorite products to your cart. Then, click the Calculate button, and finally jump to the payment page, you will see the information of [Select your Coupon Codes], click to select the Coupons you want to use, and then return to the payment page to continue to complete the payment. Please note that used Coupons will be automatically removed from your coupon.