Step 3:

Keep arms extended with a little lean at the waist to give extra momentum and force behind the throw

Shoulder Girdle - Both Shoulders are in forward rotation and are both in abduction 90 degrees from bodys Torso and parallel to the ground horizontally.  Your pectoralis Major is contracting eccentrically after release of the ball.

Elbow - Both Elbows are in extension the Triceps Brachii is contracting eccentrically and the Biceps Brachii are contracting concentrically.

Wrist - Both wrists, hands, fingers and thumbs are in flexion with the Flexor Digitorum superficialis with the flexor pollicis longus contracting concentrically.  Both wrists are in extension eccentrically contracting their flexor carpi radialis, and Palmaris Longus and Flexor Carpi Ulnaris