Your car is equipped with turn signal lights on its four corners. On the inside of your car, these turn signals usually appear as green arrows facing the direction of the intended turn.
On most cars, the turn signal lever is located to the left of the steering wheel. Shifting the lever up indicates a right turn and shifting it down indicates a left turn. Your turn signal should turn off after a turn or a lane change, but if it does not, you should turn it off manually, as soon as possible.