Listen to the sound that's playing through the equalizer. If the equalizer has a headphone jack, listen to the audio feed through headphones to hear how the equalizer is interpreting the audio. Try to identify the different instruments, voices, and sounds to determine which noises are related to which frequency ranges.
Read the knob and dial settings. The dials and knobs are labeled by relevance (low, mid, and high) or by specific frequencies. A graphic equalizer can have two to over a dozen adjustable frequencies. The knobs are turned and the dials are slid to increase and decrease the volume levels of the sounds within the frequency range. The volume is usually increased on the knobs by turning clockwise and increased in the dials by sliding up, while the volume is decreased by moving the knob or slider in the opposite direction. The higher the volume is on a knob or dial, the higher the volume is for the particular frequency range and the louder the instruments and voices in that range will sound. For example, a graphic equalizer with six dials may have the lowest three turned up and the highest three turned down to accent a string bass over a violin.
Read the volume meter. Some graphic equalizers have volume meters that compare the volume levels across the different frequencies. The volume meter shows the output volumes of the different frequencies that the knobs and dials are used to alter. The volume meter can be used to compare the adjusted volumes and prevent audio peaking. Volume meters often are color-coded. When a level on a volume meter turns red, that means the audio is too loud for the equalizer. Peaking can be stopped by lowering the volume on the knob that corresponds to the peaking frequency range.