Grasp a barbell at around shoulder width apart using an underhand grip (palms facing up).
Stand straight up, feet together (you may be more comfortable putting one foot back for stability), back straight, and with your arms fully extended.
The bar should not be touching your body.
Keeping your eyes facing forwards, elbows tucked in at your sides, and your body completely still, slowly curl the bar up.
Squeeze your biceps hard at the top of the movement, and then slowly lower it back to the starting position.
Repeat for desired reps.