Powering Up Poseidon

Powering Up Poseidon is an event quest in Fallout 76.

Detailed walkthrough
First make sure your stocked up on Stimpaks, Rad-X, Radaway, and plenty of ammo. Although the scourage inside the building are easy to kill there's a lot of them as well as machine gun turrets. (Note you do not need any materials to repair anything)

Most of the entrances are locked, needing a level 3 hacking level to get into the reactor. An easy way in is through the cooling towers or, if you go behind the facility, there is an open door leading inside. If you choose to go through the cooling towers this is one of three areas you must fix. Pipes that are emitting smoke are the ones you must fix; there are also control panels that can be fixed as well.

Next, through the cooling tower, should be a door to the generator room. Here many of the consoles are near the yellow generators. Fix those and you can move onto the next stage. Nearby should be the reactor; make the proper repairs (more Smokey pipes and consoles). Once that is all completed you can power up the reactor, ending the Event.