Turn on the electronic tuner.
Place the tuner where it can easily pick up the pitch you want to identify. If you can't get the tuner close to the sound, sing the pitch into the tuner.
Watch the tuner's indicator needle. It will point to the pitch you are singing. If it is between pitches, the sound you are trying to identify is what is called microtonal, that is, it falls between side-by-side black and white keys on a piano.