Enable the power via the power switch underneath the stairs

How do you complete "Enable the power via the power switch underneath the stairs"?

This is step 4 of 4 in Flickering Threat, given by Celeste. It is completed on Dam Battlegrounds. The exact location is marked on the Dam Battlegrounds map.

• Flickering Threat
• Dam Battlegrounds

What are the other objectives in Flickering Threat?

Flickering Threat has 4 objectives in total: Find the Generator Room, Repair the Generator using 4 Wires, Find the Ventilation Shaft and Enable the power via the power switch underneath the stairs.