Trigger the Gala Event

 is a quest in the Fallout: New Vegas add-on Dead Money.

Quick walkthrough

 * Once you have placed all your companions (Dog/God, Christine, and Dean Domino) into their quest specific location, you must activate the Gala event.
 * This requires you to activate the switch in the bell tower, in the north section of Salida del Sol. You will have to fight numerous Ghost People on the way and inside the tower.
 * After triggering the Gala Event, Ghost People will pour into the courtyard below the Bell Tower and you will have to fight or run your way back to the fountain, to the entrance of the Sierra Madre Casino.

Detailed walkthrough

 * Father Elijah will tell you the only way to gain access to the casino is to 'Trigger the Gala Event'. This will have required you to place you companions in 3 spots located around Sierra Madre, during their quests: Fires in the Sky, Strike Up the Band and Mixed Signals.
 * The Quest will then start and will marker the Bell Tower where you must enter Salida del Sol and make your way through numerous Ghost People to get to the courtyard, from there you must follow a one way route to get to the top of the tower.
 * There will be a console by a window facing the casino, once activated, it will reward you with a achievement: Having a ball and the casino will come to life with fireworks, music and lights. But it also gets the attention of the Ghost People which flood into the area below.
 * It would be wise to note that you can shoot down at the Ghost People with an Automatic Rifle or Holorifle from the windows in the tower, this should make things much easier when making the way back. But beware as they will throw spears at you, and they have a very good aim.
 * In the bell tower you can find the vending machine password for Super stimpak (Fallout: New Vegas) and for the Holorifle focus optics mod.
 * Then finally you must fight or run back the way you came, to the central fountain, and enter the Casino by the gate just behind it.