This Trophy is for putting an enemy in a locker. This is one of the most basic actions in the game, so you should definitely become familiar with it. The first opportunity to do this is at the beginning of the Tanker chapter.
Enter the interior of the ship through either the right or left doors. Now find an enemy and knock him out with your tranq gun. Take your finger and quickly press it against the screen where your weapon icon is. This should unequip your weapon. Now press the square button to pick up the enemy, and drag him into the locker area. Press the triangle button next to one of the lockers, then pick up the enemy again and drag him into it. You should automatically close the locker and earn the Trophy.