What is Centre frequency in EQ?
As it pertains to equalizers the center frequency is the exact frequency to which the EQ filter is tuned. Equalizers are filters – at least analog ones are (most digital ones are programmed to emulate filter behavior).
How do I choose EQ settings?
Normally, you'll find whichever EQ point is closest to the frequency you want to boost or reduce, and then simply move it to the exact spot you'd like for the desired effect. Turning the boost or gain knob up or down determines how much you are boosting (or reducing) your chosen frequency in decibels.