While playing on the "House" map in Casual/Ranked Multiplayer or Terrorist Hunt and you are attacking, go to the back of the house. Use your grapple hook to reach the roof, then go to the master bedroom window on the right with the yellow "XX" on the window. Break the window and enter the room. Go to the back of the bedroom and look for a square tile with metal around it on the floor. Use a breach charge on it to get the "Death From Above" achievement.