Start by sitting on a bench or box with the bar resting on your knees. Your feet should be flat on the ground, about hip-width apart.
Place your hands on the barbell for support, and lift your heels off the ground.
Hold this position for a moment, then slowly lower your heels back to the ground.
Guida Esercizio Smith Machine Seated Calf Raise - Allenamento Calves | MuscleWiki