Insert the top on the PEX about the top in the fitting. Slide the end of your PEX tubing which has the crimp ring or cinch clamp on it in excess of the end of the fitting that you choose to screwed on to the copper tubing. Press it on https://devendrat630ehl1.bloggazza.com/29747890/the-5-second-trick-for-1-2-copper-90-elbow