Repairing a window screen is a handy skill! You'll need some replacement mesh, a spline roller, and possibly a new spline. Start by removing the screen frame from the window, then pull out the old spline with a screwdriver. Lay the new mesh over the frame, press the new spline into the groove using the roller, and trim any excess mesh. Have you tried this before or is this your first time attempting a screen repair? I'm here if you need more tips!