This trophy can be done on any episode in game, but is easily done as early as Episode 1 - Back to School. After making your way off the rooftop and making your first arrest warrant, you can now switch to your T62 CEW (Tazer) by using the menu at the bottom of the screen. The sight on this weapon is a white circle, and has 2 green circles inside if your within range of the enemy that you are aiming at.
Sneak up on 5 enemies and taze them using this weapon in order to unlock the achievement. If you do get seen, you can still taze enemies, or restart your checkpoint.