In order to redeem the coupons, you must first reach NPC Gato. Players can find Gato in either Odellia (located to the left of the bell structure and fountain) or The Port of the Winds Center - The Floating Island.
Then interact with Gato and select Coupon from the Menu
Then after selecting the Coupon option, another Menu should appear. Please select "Redeem Coupon"
At the next window select "App Coupon" on the top left.
After selecting "App coupon", they click on the light green Redeem button.
Then a small window should appear where you can put the code.
If you have any issues, please contact the Warpportal Support team and submit a ticket.
Please be aware that some coupon codes have a set requirement to be redeemed like character's levels.