After the start you'll need to watch a long introduction. You can learn the controls in that time.
Look around (Y/Triangle) and go through the crowd pushing B/O. The voice will explain the differences between Low and High profile (push the right trigger/R1).
Do the same thing near the man but try to grab him using B/O. Now you need to learn how to run - simply push right trigger/R1 with A/X.
You need to learn how to assassinate guards stealthily. Stand close to your target, target him with left trigger/L1, choose the hidden blade (up), and kill him (X/Square). 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 (A/X). At the end use the eagle vision by pushing Y/Triangle.