Present your coupon when ready to use.
Tell staff that you would like to use it at time of checkout, present the JAN code and they will scan it.
Present the coupon image when entering the restaurant or when ordering.
Some coupons, such as those from Don Quijote, have the coupon JAN code on a different site. In that case, click on the coupon image, go to the page, display the coupon JAN code, and present it to store staff.