Place a flat bench underneath the bar of the Smith Machine. Adjust the barbell so it's at a height you can reach when your arms are almost fully extended. Load the plates onto the bar: 10 pounds is a great starting point. Beginners should start with just the bar and gradually add weight as they become familiar with the movement.
Lie down on the bench so the bar is over the middle of your chest. Grip the bar slightly wider than shoulder-width apart. Your palms should be facing out. Unlock the bar by lifting it up and toward you. Hold the bar with your arms straight.
Inhale and lower the bar down to your chest. Hold for one second. On an exhale, push it back up to the starting position. This counts as one rep.