This is story-related and unlocked during Act II of the campaign. It can't be missed.
Once you are given the skiff you'll be asked to find two Comm Towers to triangulate a position for the laboratory you're looking for. One - known as the East Tower, is right on the east side of the map, and, well, you can probably guess where the North Tower is. Enter the buildings, clear out a nasty or two, and get Jack to turn on the power.