Did you get the towing package, or is it standard on your model?
I ask because gen 4 models have a connector in the left kick panel for a brake controller. It's just plug 'n play. I had to attach the holder under the dashboard, not another place to put it and it was recommended by the controller.
I use a well known and recommended Tekonsha Prodigy P2 Controller.
TEKONSHA (They have fit guides and video support)
The operation is pretty simple.
When the controller is set up, when you start the car the display will show "nc" if there is no trailer connection or "c" if there is. When you step on the brake, with trailer connected, the display will show you a number that corresponds to the amount of pressure being applied.
You get everything hooked up and then set the controller (scroll wheel) to a midpoint number. Drive with the trailer, preferably on a gravel road but any low traffic road will do. Apply the brakes and see how the trailer responds. If it's squealing tires / spitting gravel you want to go to a lower number. If it doesn't seem to be working go to a higher number.
The Tekonsha has a lever on the bottom for a temporary increase. You can move the lever with your thumb to apply more braking pressure without changing your default setting.
When I'm not using my P2 I just disconnect the plug and remove it from its holder. I keep it in the center console.