If you have an acoustic guitar, you will need to use the tuner's built-in microphone. All you need to do is place the tuner close to the body of the guitar and pick each string.
Pick each string cleanly. Do not pick the string aggressively, because an incorrect reading will be given. Sometimes the needle of the tuner’s meter or the lights will move unevenly and make the tuner difficult to use. This can be caused by several things: