This requires you to locate a carepackage dropped from a plane and loot the suit or loot it from a downed player by you or someone else. If you really want this achievement, make sure to check any player box (which is left behind if a player was killed, by you or another player) as the body of the downed player vanishes soon after death, so you won't be able to tell what the player wore. There might just be a ghillie suit inside, you never know. Some players might not have looted everything from the box or even at times anything at all.