Throttle or collective?
In a real helicopter the Collective is used to raise and lower the aircraft. The throttle is used to provide power to keep the blades spinning while they do the work. They are operated by the pilot's left hand - collective on a large lever and throttle like a motorcycle throttle grip on the end of that collective lever.
With R/C helicopters, the two are linked electronically so that they are activated with the same (usually the left) stick. We usually refer to it as "throttle" cause that is the name of the stick in airplane terms. But, we are actually inputting both to give us the required lift and the engine power to maintain the rotor RPM at a constant rate.
I don't know of a flight Simulator that allows you to operate them independently. That is too much work for an R/Cer.
The Great Pumpkin