Connecting a HRV to a furnace

[I am]

Which wire should I connect from my Lennox G61MPV to the VanEE H190 so that the HRV will be working at full speed only when the furnace is working?

I know the G on my HRV is the one for high speed, but which one should I choose from the furnace control board?

Thanks.

P.S. I only wish to have the HRV working when the furnace is working.