You need some keys.
Get the dayroom key out of the safe (the combo's on the first page of the thread if you can't work it out).
Go to the door opposite the one I called out as the kitchen, then run through the resulting room (up to you if you avoid the nurses or get railed by them, but I know what I'm here for)
Run to the very last cell on the bottom (mesh floor, shit hanging from the ceiling). Snag one of the hooks in here.
Go back to the previous room, activate the hole in the floor to use the hook to fish out the kitchen key.