After the start you'll need to watch a long introduction. You can learn the controls in that time.
Look around (Y/E) and go through the crowd pushing B/Shift. The voice will explain ythe differences between Low and High profile (push the right trigger/RMB).
Do the same thing near the man but try to grab him using B/Shift. Now you need to learn how to run - simply push right trigger/R1 with X/LMB.
You need to learn how to assassinate guards stealthily. Stand close to your target, target him with left trigger/F, choose the hidden blade (up/3), and kill him (X/LMB). You need to climb the ladder when the indicator starts pulsing red. Hide in the garden on the roof.
Use blend to go past guards (X/LMB). At the end use the eagle vision by pushing Y/E.