All you need to do is equip the Halo topper, seen below, and win a match on Starbase ARC. Just in case you can't see the image, it's the gold ring like an angel, not Halo as in the franchise. If you don't have one, keep playing matches and hope it drops.
Exhibition is the fastest way. Change settings to:Game Mode:
No botsMutator ---> Max Score:
Pick a team then score the ball to unlock the achievement. https://screenshotscontent-t5001.xboxlive.com/00090000023b0c...