Your name is Cash. Your target is to kill your boss, but before you can do this, you need to eliminate all guards. If guards hear you, they will run towards you and kill you before you even use your weapon. So try to keep off their radars.
Use your ARROW KEYS to move. To walk quietly press and hold SHIFT KEY. Press "Z" KEY to use your weapon and kill the guard. Remember, you have to be gehind the guard to kill him. Good luck!