If you purchased a full Fluid Running H2Go System and Digital Bundle, you will have received a coupon for a 4th workout.  Search your email for "Fluid Running Coupon" and you'll find the code.  If you are logged in to FluidRunning.com, add a workout to your shopping cart from the Fluid Running H2Go Workout Store, and when you are at the checkout, you'll see the coupon for the free workout.