To use this Shure SM58 wireless microphone capsule, simply connect it to your compatible audio device. Make sure the connection is secure. When using it, keep it at a proper distance from your mouth to get the best sound quality. As for the rust on the grille, it doesn't affect the basic function, but try to avoid using it in a very humid environment. To maintain it, clean the surface gently with a dry cloth regularly. If you have any other questions, feel free to contact us.