During the second part of the mission, you will be walking inside the forerunner structure by moving between large pylons with circular platforms. Too help orient you, fight all the way until you get to the final platform with the elevators. Two hunters will descend. From that point, turn around so you're looking in the direction in which you can. Go back one pylon structure then turn right. Cross that bridge to that pylon. The terminal is located around its circular base.
4th Checkpoint and orientation edits. - "xl Mr 1102 lx"