Read this again, sitting in front of the computer, do the exercises in the air. Do it a couple of times. Then when you go to the gym, you should be able to duplicate them. Does this make sense? I hope it helps.
This is a great warm up before any upper body workout. It takes only 3-5 minutes once you get the hang of it, and it can save you problems later. IF, however, you already have a problem, try to get help from a good physical therapist or orthopedist and an okay before you go at this. You could even go as far as to print this out for them and ask if it's okay for you.
Shoulder Relief by Dr. Jen: a 45 minute comprehensive shoulder-safe workout to strengthen and prevent injuries to the shoulder!