Step 1: remove factory wind deflector
Begin by jacking the rear of the car up and removing the rear wheels. If you look in the rear wheel well, facing forward, you will notice the factory wind deflectors. These are attached by four Phillips head bolts (they can be stubborn so make sure not to strip the head). Removing the four bolts drops the wind deflector. Attach the rear brake duct in the same mounting holes, using the provided M6 x 1.00 screws.
Step 2: Attach hose to dust shield
I found the best spot to attach the aluminum flange to the dust shield to be on the lower portion. These keeps a nice straight route for the hose and is easy to route around the rear wheels. Using a hole saw drill into the dust shield and attach using button head screws and nuts (I prefer to use M6 here, but a similar size works). Then connect the hose from the brake duct to the aluminum flange on the dust shield.