Measure the size of the glass that needs to be replaced. This should match the original glass as closely as possible in terms of width, height, thickness and any additional coatings applied to the original glass. Order the replacement glass from your local home improvement store.
Remove the window frame from the opening by twisting or turning the slider mechanisms on the window then pulling the sash outward. These mechanisms may vary in different types of windows
Lay the frame on a padded surface, such as a tabletop covered with a blanket. Remove the butyl seal from around the glass with a utility knife. Scrape off all pieces of the sealer from around the frame.
Use a hacksaw blade to gently work the glass out of the frame. Remove the screws that hold the glass in the frame and set them aside. Remove all broken shards of glass from the frame and discard.
Clean the new glass with a solution of isopropyl alcohol, vinegar and water to remove all dirt and grease. Mix 1 cup of isopropyl alcohol, 1 cup of vinegar and 1 cup of water thoroughly. Pour the mixture into a spray bottle and clean the glass, especially around the edges where fingerprints are prone to show up. Then apply a thin bead of silicone around the frame.
Mount the replacement glass into position inside the frame and ensure that the spacers are properly placed to hold the panes apart.
Replace the butyl seal around the glass then caulk around the window with silicone sealer.
Wait for the sealer to dry for 24 hours before re-installing the window into its opening.