This achievement is simple enough; at the main menu, press Multiplayer, custom game, then
to invite people to your squad. Simply have someone join, play a game to completion and regardless of if you win or lose, you'll unlock this achievement.
However, if you are really unlucky as was I, you may experience a bug where every time you press
to invite people or press onto custom game, it would freeze your game. Regardless of playing with a digital or physical copy, on a 360 xbox one or series x/s, it would just freeze the game up. Trying on many different days and with different people, I simply could not prevent the game from crashing on me no matter how hard I tried. If you experience this weird bug, I have great news for you ( : the way to save your profile and get this to unlock is to remove people from your 360 friends list and delete messages from your inbox. I had a full list of 100, which I brought down to 70, and spammed myself with messages until the loading messages glitch occurred to which I then deleted them all from my inbox. I was then able to launch the game and make a squad.
If you play this and experience constant crashing and freezing, especially when a round ends since this bug also causes that as an issue, just remove people from your friends list and delete messages and it should clear the bug out. Hope it helps someone out as these servers close (: