Turning on is as easy as you would expect. Open the first two doors and on the right, in front of Double Tap is the building where there is the power switch.
Next to the power switch is a locker with a key inside it.
This key will grant you access to 2 different places :
The way back to spawn, where you can also find Juggernog
The door in the Police Station which is for the Private Collection side easter egg
To unlock Pack-A-Punch, you must first turn on the power.
You now need to go to Water Refinery, at the opposite side of the road in front of Power Station.
Then interact with the computer.
You can now open the way to the sewer in the middle of the Main Road. Once the gates are opened, go down the sewer and the Pack-A-Punch machine will be at the end.
You might have notice that there is a Token counter, in addition to the credits counter.
These tokens are the currency of the Trader pod. Trader pods can be active in 2 locations :
After the first door at spawn
At the first floor of Police Station