Using online coupon codes or promo links when shopping online is similar to using paper coupons or shopping the sales at local stores. But unlike paper coupons that you hand to a cashier to redeem, online stores have a code to enter during checkout that relates to a specific discount and that amount is subtracted from the total purchase. The discounts range from dollar-off savings to free shipping.Depending on the online store, there are a few different places to enter coupon codes. In some cases, the coupon can be entered in the shopping cart, before checking out. Other times, the coupon is entered on the order review page prior to checking out. Look around carefully for the coupon code (also called promo codes) "submit" area before completing a purchase from an online store.