Halo: The Master Chief Collection - Halo 2 - Determined - Halo 2: Activate Terminal 8 on Sacred Icon. This achievement is fairly easy to unlock.
On the mission Sacred Icon, midway through the mission you drop down a series of pipes to an open area where the back is open to the outside area of the mission.
The terminal is located on the right side of the room in between the wall and a pillar/wall.
Run over and interact with it and your achievement should pop! Enjoy!