Halo: The Master Chief Collection - Halo 2 - Examiner - Halo 2: Activate Terminal 3 on Metropolis. This achievement is fairly easy to unlock.
On the mission Metropolis, near the end of the mission you must defeat the two wraiths and any enemies in the area.
After they are defeated the marines will open the door and come out to you.
Run inside where the terminal is located at the end of the hall on the left.
Run over and interact with it and your achievement should pop! Enjoy!