These are some CV injection points of the Poly-61. You need to connect the CV with an additional resistor. Try 100k.Decrease the value for a stronger effect and increase it for a weaker influence.
If you connect one side of the potentiometer to +15V and the other one to -15 you can adjust the value up and down with the center position as default. In this case use the following resistor values:
Res: 330kAttack: 330k
MG speed: 220k
These give you about the same range as the original controls.
In case you are using the CV outtputs of the ModyPoly, connect a 100nF capacitor across the negative input and the output of the opamp to filter out high frequencies.
This is not tested but I am pretty sure it is working.
[edit: Cutoff, resonance, attack and decay work very well. Very complicated to add control to the other parameters]