There are lots of entrances but the easiest way is in a small hall. As you walk down the entrance in big letters it will say "Dire Maul". when you come to a big door theat is just blank, turn right and you will find a small passage and go down that and there it is. You can also go into the Dire Maul courtyard and on either side is a door that you need a Cresent Key for. The other entrance is north of Camp Mojache in "Lariss Pavilion" go down the structure and the is a door you will also need the key...The frst one dosen't require a key

http://wow.allakhazam.com/db/qlookup.html?zone=85

that is where you wanna go I belive :D