How to get a Steam Key for Flying Circus?

[ClienT8832]

I have searched these forums and the internet, but have not found a clear answer to my question:

 

I purchased Flying Circus Vol II several years ago from 1C.  How can I get a Steam Key for this game?

[Patricks]

By purchasing it from Steam? 

[=IRFC=Gascan]

I'm pretty sure there's a way to link your steam account and your account from the IL2 store here, but I don't know how.