1. Turn on your guitar tuner.
2. Play the A string on your guitar.
3. The tuner will show you whether the string is in tune or not.
4. If the string is too sharp (shows +), turn the tuning peg for the A string counterclockwise.
5. If the string is too flat (shows -), turn the tuning peg for the A string clockwise.
6. Repeat steps 3-5 until the tuner shows that the string is in tune.
7. Once the A string is in tune, you can tune the rest of the strings on your guitar using the same process.