You will unlock this trophy upon abducting Anton Sokolov in mission four. Impossible to miss.
Your objective for mission four is to make your way to Anton Sokolov’s House, where he is residing. Once you reach the area, you must search for him as there is no marker on screen. He is located at the top of his house, in a small room accessible via outside stairs. Once you locate him, either choke him or shoot a sleep dart at him. You must knock him out rather than kill him. Once he is unconscious, pick him up and make your way out of his house and towards Samuel to end the mission.