Locate the small tab on the underside of wiper blade (near where the rubber insert meets the metal arm), then push it in (or in some cases, pull on it) to release. Pull down on the blade and it should then slide off the hook of the metal arm.
If the left and right wipers are different sizes, be sure to match the new wiper to the correct side. Push the movable hinge on the new blade until the hinge is perpendicular to the rest of the blade.
Push the metal hook through the hole in the blade.
Gently push the blade back down to a resting position against the windshield.
If the wiper arm angle is off it can cause chattering. The rule of thumb is that the blade is 90 degrees to the glass mid-swipe The reason for mid-swipe is it will change angle from the top of the windshield to the bottom of the windshield due to the curvature of the glass.
If the new wipers are streaky, first try cleaning the rubber insert with alcohol wipes or a cloth soaked in mineral spirits. If the wipers are still streaky, check that the blades are properly installed. Verify that you’ve installed each blade on the correct side and check that the wiper is properly oriented. If all else fails, stop by your local auto-parts store for help.