GHC supports Concurrent Haskell by default, without requiring a special option or libraries compiled in a certain way. To get access to the support libraries for Concurrent Haskell, just import Control.Concurrent (details are in the accompanying library documentation).
RTS options are provided for modifying the behaviour of the threaded runtime system. See Section 4.12.4.
Concurrent Haskell is described in more detail in the documentation for the Control.Concurrent module.