Hi,
Actually, it's very easy and there is plenty of official actions that do that already: example: ApplicationQuit
ApplicationQuit is your typical simple action that calls a static method. in this case it calls a Unity Class called "Application" and specifically the static method "Quit()"
So TWO VERY IMPORTANT THINGS:
--note that the call to the static method is done within the "OnEnter()" function, it's important to do it within that function for the action to work.
-- Also note that after you are finished with what the action is supposed to do, you need to call the function "Finish()" which is part of the way actions are supposed to work, this tells PlayMaker engine that your action is done, it helps figuring out if the state is finished ( can thus call the "FINISH" system event we all know)
Does that help?
bye,
Jean