First be sure to place yourself in a quiet environment.
Use a headphone; you should only hear your tinnitus and the frequency test.
Play the synthesizer ( PLAY / PAUSE) and adjust the volume to your convenience – ideally at the same level as the perception of your tinnitus.
In the case where you would have several tinnitus, focus on the one you most perceive.
Then vary the frequency using the previous / next arrows, until you find the frequency that best matches your tinnitus.
Do not hesitate to pause / play the sound in order to compare better.
Take your time to be as sure as possible.
Frequency range of the tool goes from 78Hz (D#1) up to 9956Hz (D#8). The frequency area covered represents 7 octaves. If you are not familiar with these concepts, we invite you to read our post dedicated to Frequencies and Decibels.