How to compute for the capacitor to achieve a certain cut-off frequency?
There are three cascaded high pass filters in that circuit.
This means that if you set the cut-off frequency (-3dB frequency) of all three RC filters to the same frequency using the standard formula fc = 1/(2piRC) then the overall response of the complete circuit will be -9dB down at that frequency.
To get an overall circuit response of -3dB at the required frequency you must calculate the capacitor values to achieve a -3dB cut-off frequency of each of the three filters, using the equation in the paragraph above, and then double the values of all three capacitors.
By doubling the capacitor values we are making Capacitor Reactance, Xc = R/2 at the overall -3dB frequency.
Where R is the resistance associated with each filter.