To find your zones click on a workout in the “Calendar” view. This will bring up a pop up window. Then click the “HR Zones” tab. If you use a heart rate monitor that is compatible with the log (check here) you can upload your workouts to the log and the HR Zone information will automatically be filled in for you.
FYI: HR zones are customized to the type of exercise. For example run HR zones tend to be slightly higher than bike zones.