I've been struggling with this a bit too. as Dpyle said, forget about heavy weights ffor now and focus on form. Using light weights, pulling with your shoulder blades, to the point where you are almost pinching them together in the back, then hold, then slowly release. try doing this in slow motion. if you do this correctly, within a few reps, your muscles will begin to burn. this is a clue you are on the right track.

Good luck!
---Roman