Where do I turn the power on in this tower?!

[Disguised Poison]

I recall I had the same problem the very 1st time I played this game. I just couldn't find the bloody power switch.
Map look: https://steamcommunity.com/sharedfiles/filedetails/?id=2214827813
A look to the bridge: https://steamcommunity.com/sharedfiles/filedetails/?id=2214827845
I hope you know which tower I'm talking about.

[D'zen]

There is a structure down there on the ground, right next to the tower. You have to go inside and turn it on.

See that square on the top of your minimap on the second screenshot? I believe this is it.

[Disguised Poison]

Thanks for replying D'Zendra. But I have been to that small room at the bottom of the tower you mentioned, and I only found one fuse box.
I guess I need more "accurate" directions to find this mystery power box.
I cleared the area of zombies, but there is this notification appearing from time to time telling me to turn on the power. Fortunately one can climb pretty high up the tower, volatiles just won't go that high. But it would be nice to finally solve this mystery.

[StinVec]

It looks like you climbed one level too high up the tower. The guide icon says the switch is below you, so you need to find your way to the floor below you.

Make your way to that floor instead of to the very top and you'll find a row of power boxes and one has a switch you can flip on it. Instead of staying on the interior all the way to the top-top, you may need to step out to the exterior of the tower part way up by stepping onto the round metal thing on the outside to then be able to climb up to that floor and climb over its railing.

[Disguised Poison]

Now you're talking! Thank you so much SV! :)
I'll try that right now!

[StinVec]

I'm glad to try to help! I hope I'm accurate to how that floor is reached as it has been a long time since I did that quest and I'm going from memory.

I recall there being yellow/black grab holds on the outside that can be used to reach that floor after crouching under the angled support beam at a mid-level floor and stepping to the outside onto the round metal thing. That might have been someplace else, but I think that was here.