Stretch out calves prior(check lower body stretches video) and sit with your thighs under pads. Your toes and front part of your foot should be hanging off of the bar beneath your feet. You want to raise your feet up as if you were trying to stand on your toes which then will cause you to use your calves. Repeat this for at least 15-20 reps for 3-4 sets. Use lighter weight for definition and heavier weight lower reps(6-10) for building size.