In Mission 1: The Cleaner, after getting the assault rifle, you will have to hold off enemies while your robot opens a door. You will get a tutorial prompt about door panels at this point. Five enemies will spawn really close together in this area. They are coming down the stairs. Once they stop walking, use the drone by pressing Triangle to shock them and get the "Dark Forces" trophy. Restart the checkpoint to try again if it fails. The droid can be used as soon as the bar at the bottom of the screen is fully charged.