To get your Coupons codes I suggest browsing the active Evil Hunter Tycoon Reddit:
Once you have your coupon code you can get your user code from the settings. (Keep this user code private)
Once you have your User code you can click the coupons link:
After you click the coupons link you’ll arrive at this page, and you can enter the Coupon code you got from the Evil Hunter Tycoon Reddit page.
Make sure to select the proper game, and enter your User code in Uppercase to prevent any errors.
Once you submit you should have received your reward in your mail box in-game.