S2 M3: The Hookblade - Assassin's Creed Revelations
When you return to the HQ Yusuf is waiting -- and the first thing that he asks is where is your Hookblade? Of course not being from this city we do not have one -- so he gives us one! With the Hookblade you can zipline and other things -- in fact to gain 100% Synchronization you will need to successfully do each of the following moves with it:
-- Use the Hook to climb
-- Use the Hook to extend your reach in a jump
-- Use the Hook to snag one of the swinging objects
-- Do four Hook-n-runs
Basically you just need to follow Yusuf and do what he does, and you will easily unlock 100% Synchronization.
Learning to use the Hookblade
Near the area you are in when you end the memory there is a closed Tailor Shop -- you can invest 900 coins in reopening it, which will increase your income by 1750 coins every 20 minutes. I mention this because as mentioned previously, getting your income up is critically important to success later in the game, so the faster you manage to do that the better off you are and the happier you will be... So go ahead and find that shop and re-open it now!
You may also want to seek out the Blacksmith and have your armor repaired now before you begin the next memory.