There is a black o-ring that you turn to release the bulb, once you turn it you may have to jiggle the bulb a little to pull it out. I find it easier to unplug it first then turn the o-ring.
the front bulb needs to be replaced.
Pull away the black plastic cladding in the back rear corner of the trunk that covers the rear light housing, the turn indicator bulb is the bulb closet to the side of the car, turn and pull the socket and bulb out of the housing, turn and remove the bulb to remove from socket.
Starch.
Rusting
It could be the bulb that is burned out, but more than likely it is the socket the bulb connects to.
Check to see if the brake lamp and turn signal lamp are the same bulb. If so, its a bad bulb. See sources and related links below to lookup bulb information.
Mold
Incorrect size bulb installed.
Gravitation.
An open ground or a short to ground when the signal is on. Usually a bad bulb.
Brake dust!