Using your other hand, you can secure your lower arm in place.
Keeping the weight parallel to the floor, turn your wrist inwards then outwards.
Keep the movement smooth, and as large as possible, keeping the forearm on the bench.

BEGINNERS
Aim for 5 lifts with light weight. Repeat twice.
INTERMEDIATE
Aim for 10 lifts with medium weight. Repeat twice.
ADVANCED
Aim for 20 lifts with suitable weight. Repeat three times.
Tutorial provided by netfit