You didn’t receive the actual pen. You received a “pen” to push into the cartridge and reconstitute it. Once this is done, that piece is useless to you and you’re left with your cartridge with reconstituted hgh. Use your slin pins to draw from the red stopper just as Achilles said. To calculate your dose you will need to find the total volume of the liquid (2 or 3ml I believe) and divide your 72 iu by the volume to see how you need to dose. I use these as well but I have the actual pen to put the cartridge into that I got back when I had a script for this stuff. Email Pharma Hgh and he will tell you exactly how to dose with slin pin