In the mission War Games, you first have to meet up with Captain Gorah in Operationsroom.
But where is this operationsroom then ? I looked on Deep Space 9 in the place you get beamed down to in Deep Space 9 Fleet Action, the operationsroom, but couldn't find any captain Gorah.
Captain Gorah is not in the DS9 fleet action. You have to pick the other option to go to DS9 normally. Also once you are in the normal version of DS9 you have to use one of the elevators in the center ring. There will be prompt labeled turbolift to operations room.