The brake light is accessed through the trunk. Remove the plastic covering the corner of the inside of the trunk. Once that is out of the way you will see several 10mm nuts. Remove these nuts and pull the light away from the vehicle. Twist the bulb socket out of the lens and replace the bulb.
I assume you are trying to change the headlight bulb and not the entire headlight. To change the bulb follow the directions below. It is a tight fit, but you shouldn't have to remove any parts to get to the cover or connector. Once you can access the bulb, there is a small spring clip that holds the bulb in place. You need to move the clip from under the tab to release the bulb.