To replace a wooden window screen, take out the window frame from the window, and remove the old screen using a pry bar. If there is a wooden molding strip holding the screen in place, remove it without damaging it. Cut out the screen to be slightly larger than the frame, and place it over the frame. Attach the screen to the frame using a wood stapler, remove the excess screen with a knife, and put the molding in place.
To replace a metal or vinyl frame screen, remove the window frame, take the old screen off the frame. To remove the spline or black rubber seal, find the end of each piece, pick it up using a screwdriver, and pull it out. If the spline is undamaged, use it again later instead of buying a new one. Lay the new screen on top of the frame, place the spline on top of the screen to go around the perimeter of a window frame groove. Push the spline together with the screen into the window groove using a putty knife or a spline tool. After pushing one side of the screen in place, pull the other end of the screen, and push the other sides into the groove. This guarantees that the screen is going to be tight on the frame. Cut off the excess screen, as with the wooden window screen.