Choose the appropriate weight dumbbells. Grab the dumbbells using an overhand grip. Kneel on the floor and put your forearms on the bench (at shoulderwidth) so that your wrists protrude from the bench (palms down).
From the starting position curl the dumbbells by bending your wrists upwards while contracting your forearm muscles. Do the required number of repetitions. Exhale while your wrists are moving up and inhale while they are going down.
Keep your torso upright and do not bend your chest (do not make a hunch).
Start with lighter dumbbells.