Go here, click "Sign In" and log-in or create an account, if not already signed-in. Return to their coupon page and click "Get My Epic Coupon". Once claimed, go to Tropico 5 for PC and click "Get" for free. Place the order for the free Tropico 5 at $0.00. A $10 off $14.99 coupon will be applied to your account.
Browse their list of games and find something to buy. The $10 discount applies only to the purchase of a single title priced $14.99 and up. For example, Among Us All-in One Pack for PC for $15.49, or $5.49 after $10 off. The popular multiplayer Among Us game is free on mobile devices, but costs money to play on a PC. Grand Theft Auto V for PC for $14.99, or $5 after $10 off.