From the main menu simply navigate to the "Campaigns" section then go into the "Training Prologue" scroll across to "Freeform training" Select and play.
The fastest way I have found for this map (Without being caught) is to use Terry Norfolk (Man in white suit) to attend a meeting with Kalvin Ritter (Target) as its an easy Silent Assasin.
Easiest way to get his disguise is to use the coins on the box in front of you at the start, lure Norfolk over to your start point and knock him out. There are no enforcers or real limitations for Norfolk, so just walk aboard, talk to Ritter and then go to his office and kill him however you please.
Go around to the opposite side of the office climb out the window and leave the ship, once off the ship turn left and head over to the exit car. Hit the button to end the mission.
Exiting the mission will pop the achievement.