You cant. If you try, the second 555 will stop oscillating. Try it with a 1K or 5K Pot first.
Ps, I just checked it. It looks the 555 will oscillate if the control voltage is from 0.1 to 11.9V when the Vdd = 12.0V.
Here is how I would do it: The amplifier has to both source and sink current from the Control input to 555. It is easier to do this with an opamp than it is with a transistor. The voltage gain of the opamp is just under 3, and the two 100Ks bias the input midway with respect to V(rc). The opamp does not load the RC timing network of the first 555 like the base current of a transistor would.