You need to cut the screen out with cheese wire or there is a tool you can get which you can use on your own. Once you get the screen out you have to clean all the old sealer off. Then rust proof around the screen. You stick the new screen in with tiger seal. Tape the screen in and leave if for a couple of hours. Sick the new trim in round the out side of the screen. And your done. Be better to get a pro to do it. Dosnt cost to much.