You must play in Forge with 2 people. As you get on the ghost, look up and you should see a big room.

One person gets on the turret below the room and the other goes into forge and carrys the other person up (make sure the person's body is fully in).

When the person is in you should buy 3 respawn points and a rocket launcher.

If you noticed there are 2 doors on the 1 wall. If you go out side just over the big door you should see another room and do the same steps as the first time.