What he is saying, You don't play ARMA X. When you launch ARMA X It's just extra content, the bonus content of the package. When buying ARMA X (or being gifted it) It adds these individual games to your Library: ArmA, ArmA2, ArmA2OA, ArmA:CWA. You don't launch ARMA X you launch each one of those games individually from your steam library if you want to play them.