Resonance of Fate

First you will need to get this mission. Go to the guild office and look at the bulletin board. After you get the mission, go talk to the guy outside of the guild office for the mission details. You need to restore power to the bridge.

Defeat an enemy or two to get an energy hex. See:

Once you have one, go to the world map if you are not already there and press X to bring up the hex placement screen. Place the energy hex over the white hex next to the bridge. Once that is done go back into town and talk to the guy outside of the guild to finish the mission. The achievement will then be granted.