Instructions
Start the game and start walking around the town you are dropped off in. Along the way will be a blacksmith̵7;s store. Walk into the store and follow the on-screen prompts to have him make you a retractable locking hidden blade. Leave the store.
Play the game as you normally would until you get close to your next assassination target. Press the left trigger as soon as he is in sight to lock on to him.
Walk up to him while continuing to hold the left trigger. Press the ̶0;X̶1; button (square button on PS3) as soon as you are next to him to use the hidden blade and then release the button to retract it back into your sleeve.