Straddle seat with both levers positioned slightly above horizontal. Grasp both lever ends with elbows slightly above levers. Sit down near end of seat with torso leaning forward slightly and slightly bent elbows pointing back.
Push levers downward and together in hugging motion. Keep shoulders internally rotated so elbows are pointed slightly upward at top and out to sides at bottom. Return to starting position until chest muscles are stretched. Repeat.
Under greater resistance, positioning torso at lower angle downward (by bending over at hips), will allow upper body weight to counterbalance upward pull of cables, as opposed to stepping forward and struggling with the backward pull of cables. Also see Bent-over Fly on Standing Iron Cross Machine.