Buy the correct windshield for your car from an auto-glass store.
Detach all the items attached to or near the windshield, including the rearview mirror, wipers etc.
Cover all the heater and defroster vents with paper or plastic.
Put on protective gloves, so you don't get cut by broken glass.
Check the rubber gasket around the window for damage. If it's cracked or damaged, you'll have to replace it. If the gasket is intact, insert a knife and make a slit in one corner. Carefully insert a thin screwdriver into the slit and run it around the frame to separate the gasket from the glass. Remove the gasket.
Push away the glass from the frame by gently pushing the glass from the inside. Carefully remove the glass. A windshield is quite heavy and the glass can break or shatter while removing it. You may need another person to help you with this step.
Wipe the frame thoroughly to remove all dirt or rust.
Place the gasket (the old one or a new one) around the new windshield. Place the inside of the gasket on the inside of the glass.
Apply a sealant or petroleum jelly to the outer edge of the gasket and slowly lower the glass onto the frame.
Press the windshield firmly onto the frame, making sure the gasket fits snugly.
Wipe away any excess adhesive or petroleum jelly http://4wheelonline.com/jeep/Jeep_bumpers.20737