Find room 3F | Chapter 5: The Forsaken Thief Guide

Room 3F is locked- as for now

After you walk into the [Treatment Center - Third Floor] you can immediately go South, or explore the rooms that you pass by, in the first place. Of course, this is not required but, thanks to this, you will see several interesting cutscenes. Do not worry about the fact that, for the time being, you cannot access theses room, because they become accessible only later into the exploration of this place. Approach room 3F (the South-most room), thanks to which you will learn that you need to restore power supply.