This refers to the ending part of the quest when you have to go to the Diamond City Radio Station and replace the "things" to broadcast your message to the people of the commonwealth.
This mission occurs during the institute main quests line right after "Mass Fusion".
The "thing with the tubes" goes in the smaller white machine on the right.
The "thing with the dials" goes in the middle machine.
and The "thing with the buttons" goes in the left machine.
I'm sure fiddling around you'd figure it out, but I figured I'd add a solution since I didn't see one.