on the back of the turn signal there is a hole in the fender. inside the hole there is a plastic lever to push down on to release the turn signal housing. You will need a fairly long screwdriver for this.
FYI... you need to open the hood to find the hole on the top of the fender just above the turn signal light... slide a medium to long flat headed screw driver straight down. You'll feel the plastic lever. Push down and slightly toward the front of the car. The turn signal housing should pop out.