How to perform a  barbell curl?
Stand straight, with the barbell held in the hands, arms resting. Bend your arms at the elbow joint, to lift the barbell to a flat angle, and then lower it back down and repeat.
Stand straight, with the barbell held in the hands, arms resting. Bend your arms at the shoulders, to lift the barbell to a flat angle, and then lower it back down and repeat.