If you do not have a clip-on tuner and want to use the online version, this will work but you have to use your ears to determine if the sound of your guitar is below or above the sound you hear online. Sometimes it can be difficult to tell, but if you can match the two different pitches with your voice, sometimes that helps. Again, starting with the sixth string play the note online then pluck the corresponding string on the guitar and listen. Adjust the note with the tuning key same as if you have a clip on tuner, but use your ears to determine when the two notes match. This can be tricky until you've done it a few times. When the notes are close you will hear a wavering or warbling sound which is caused when two notes almost the same pitch are played at the same time. When you hear this sound you will know you are close. Keep tuning until the warbling slows then disappears. The string should now be in tune. Go to the next higher string and keep going until all strings are in tune.