To fit replacement window panes, remove the old glass pieces, the glazing compound and the glazing points from the window, apply a fresh layer of the glazing compound on the window's sides, and attach the replacement window pane to it. Place the glazing points appropriately, and seal the window's edges using glazing compound. Finally, prime and paint the compound.
To take the glass pieces out of the window, use a pair of needle-nosed pliers. If required, cover the bigger glass pieces with masking tape, break them, and then remove them. Use a putty knife to scrape away the existing glazing compound. If the compound breaks easily, use mineral spirits to make removal easy. Take out the glazing points using the needle-nosed pliers.
Begin fitting the replacement glass by applying fresh glazing compound as a thin line on the window's sides. Smooth the compound with a putty knife. Place the replacement window pane over the compound. Position the glazing points at a distance of a few inches around the glass, and press them in place.
Again, apply the glazing compound on the window's edges, and smooth it to seal the pane. Remove extra compound, and allow the rest to dry. Then, apply a coat of primer and paint over the compound. When painting, paint a thin line on the pane to seal it securely.