Starting seated, position your foot in the middle of the platform. Your active foot should approximately be in line with your shoulder, and pointing slightly outwards. Extend your leg out past the safety locks then unlock the safeties using your hands.

Once the safeties are disengaged, lower the weight by bending your knee in a controlled motion towards yourself until your leg is bent at roughly 45 degrees. Then push back outwards, extending the knee to a point just before it's fully extended. Engage your core to keep your lower back and hips firmly against the padding. When you have completed your final repetition, with your leg extended, engage the safety lock and slowly lower the weights back down until the safety lock catches the weight.

Avoid fully locking your knee out.