First, you need the right tools and a lot of luck. Ther is a rubber moulding around the windshield that first needs removed. After it is pulled out, a special tool (blade) which is on a 90 degree is used to cut the glue that holds it in place. Go all the way around the windshield then move to a longer blade aprox 2" long. Have someone there to help as you tilt the top of the window gently forward so you can get to any glue at the bottom of the glass. You may want to remove the cowl and start at that point cutting the glue.
I realize these are basic directions, but that is how it is done.