First you pop open the lens and it's chrome surround. A flat screwdriver helps here. There should be a small indention at the very bottom of the lens chrome surround.

Once you have popped the lens off the reflector and the bulb will need to be pulled out of the housing. These usually just fall right out but sometimes need a slight bit of prying. Careful here, some of these are glass and will break. Just assume it is glass before prying on it.

Then look at the back of the reflector. It should be light green in color and have a few Bosch part number stickers on it. The bulb is held into the reflector with a metal clip. Free the clip and the bulb holder pulls straight out.

The bulb is a bayonet type, one that is easy to find at any auto parts store. You might want to get an LED not just so it will last but because it will run cooler and help to preserve the reflector's coating.

Reassembly is the reverse of what you just did.