for this you will need to know first the value of CL of the xtal , the value of the capacitors you will use are double than this value of CL , the capacitosr you wil use will need to be equal ..this is theoretical..practical ..you will use some capacitors more smalest that double ..1.5 to 1.8 X CL
You should know the Loading Capacitance or CL of the Quartz crystal what you use. Only when the Quartz crystal used in your circuit is shunt with the capacitor with the value CL can your Quartz Crystal be an oscillator oscillate at center frequency.