Check the owners manual in your glove compartment. It tells & shows you how to do it. You open the hood and stick a phillips screw driver down into a hole above the signal light. Unscrew the screw nearly all the way. The signal light (lens) should easily slide out. Turn the base of the bulb socket (with cable attached) to remove the light (socket) from the lens. Turn the light bulb to remove it from the socket. The light is a bayonette type of bulb ..... a non-threaded base with two lugs sticking out from the sides. Replace with a standard 21W bulb... I think BMW spec's a Sylvania bulb... but any bulb in this wattage range (and same size) should do. I suggest going with a lower wattage bulb if you deviate from 21W.