Step 1 : Promotion - Promotion Coupon - Generate
Step 2 : Promotion Coupon - Generate - Choose Manually Typed - after that input the Password - Generate Coupon
Step 3 : Go to SELL - Promotion Coupon - Input Coupon and OK and you can click discounts button.
Step 4 : Fill your coupon discount for unlock discount.
And you coupon will be applied in sell menu
Video Promotion Coupon - Discount Percent and Amount Type