VCO SN74LS624 - understanding pin out / how to read datasheet?
CX1 and CX2 can be used to connect to an external capacitor or crystal to set the frequency.  Figures 3 contain the information needed to select the value for the 'LS624:



If you want a 100KHz center frequency, you are half way between 10^-8 and 10^-9 F (non-linear scale, so 3.3nF is probably the right value.

If you are building this on a breadboard, you will want to stay with lower frequencies (100KHz, or 1MHz if you are bold).

(V)RNG determines the sensitivity to the FC input (slope) for the '624.  Figure 1 contains the information you need to choose this value:



For maximum sensitivity (maximum frequency swing), use a lower voltage.  If you don't need the range or you have stability problems, increase the voltage on this pin.

I think RC = RNG, the datasheet does appear a little ambiguous on this.

(credit) All pictures taken from the referenced TI datasheet.