change direction when i touch a certain object in my scene.,set an objects direction when it touches something

im making a top down 3D game and im stuck and dont know where to start. I have my guy always looking forward and when he touches a certain object i want him to change his direction to left for example. How do i do this please help.,Im making a game where if you touch an object it will change your direction. its top down and im always facing up and i want it so that when i touch a certain object it will set its direction facing left(example). I have no idea where to start im stuck, please help.