When you start this mission you will have to make a choice between convincing God to follow you, or to use the voice clip of Elijah to turn him into Dog and taking the easy option to follow you.
Once God/Dog is your companion, head east from the fountain and follow the street signs that direct you to the Salida del Sol South.
Fight your way through to the switch station. When you reach the gate, Dog/God will initiate conversation.
If you are talking to Dog, he will ask to be fed, but won't give you any more clues about what to do specifically. He will also mention the Gala Event having been switched on once before.
If you are speaking to God, he will mention that Dog knows about the Gala Event having been switched on before. You can...
Force Dog/God to obey by locking them inside the station with the terminal outside. God hints at this solution by mentioning that the locked gate would hold Dog.
Ask what God needs. He will ultimately ask for Meat from ghost harvesters, and two will spawn with quest markers. Kill them for one portion of meat each and bring it back to God. You can still switch God back to Dog, but Dog will not engage the Courier in conversation and you cannot give the meat to Dog.
With Intelligence 7, you can tell him that you can or have figured out the schematics and could walk Dog through it if God does not cooperate. God will agree to turn on the switches without any demands.
Once you have persuaded either God or Dog to wait in the switching substation, the quest is complete.