This is a retroactive achievement: if you satisfied the requirement during the period of Game Preview, it will unlock automatically once downloaded the complete game.
To unlock this achievement, you have to be the winner of a Squad Match. You can play either third-person or first-person modes. The achievement will pop in both cases.
You don't need to be alive to unlock the achievement. If your team is the last one standing, everyone in the team will we awarded with the achievement, even if one or more of you are dead.
I highly recommend to play with 3 friends to coordinate together your movements, balancing your equips, etc. If you try to find a game alone, the game will automatically match you up with other players. They can be a team made up in any combination from: a whole team of alone players like you, or a team of 3 friends. Like in the case of Duo, it's harder to win if you don't know what your allies are doing, but not impossible of course. Just remember that you will find enemy teams made of up 4 players who probably are talking each other...
There is also another way to obtain this achievement. You can enter a Squad Match with an undersized team. In the main menu inside the lobby, below Squad, you will find "1-Man Squad", "2-Men Squad", "3-Men Squad", depending on how many players are present in the lobby with you. For example, you can decide to start a Squad match with only 2 friends by chosing "3-Men Squad". In this way, you are going to face enemy teams made of up 4 players, but the decision is up to you and, for the achievement, a victory will count as well.