1-2 of 2 Answers
You can put it about 2 inches below your neck, right in the middle of your back on the spine. You should be able to press the button by reaching your arm on your back to be able to press on the button for power on/off and for changing tracking modes. Where exactly you put it on your back is not super important though, since each time you will calibrate your perfect posture in that exact moment (which can change because of the type of chair or where you are sitting)
Verified Purchase
How will this help you with your shoulder?