The discount coupon you have can be found on the [My Shopping Information > G Bankbook] menu or on the "My Coupon Box" menu on the product detail page you want to purchase.
(I can't see "My Coupon Box" when I'm not logged in.)

① Use individual discount coupons
    Click "My Coupon Box" on the product details page → Among the coupons available in the current product
    Select and apply discount coupon Click → Purchase at discount coupon application price

② Use coupons for each product on the product details page
    Click "Download Coupon" on the detailed page of the product you want to purchase →

     Purchase with discount coupon application price

③ Use discount coupons for regular customers (Only if you are a single customer)
    Enter www.gmarket.co.kr in the Internet address window or log in to the Gmarket via favorites → regulars
    Get a customer discount coupon (connection) → When clicking on the product you want to purchase, the discount price with the 

     regular customer coupon applied
    Automatically marked with → After checking the discount, purchase

④ Use mini shop regular discount coupons
    Go to Mini Shop from the seller information on the product details page → At the top left of Mini Shop
    Click to register a regular store → Click to receive a regular discount coupon from the mini shop → Purchase at the discount

Coupon priceThe discount coupon does not overlap, so please purchase it using the discount coupon that allows you to enjoy the most benefits.