On my 2015 Chevy Silverado 2500HD the integrated brake control is mounted toward the top of the dash board just left of the steering wheel and over the headlight and transfer case knobs.
There are two slider knobs . . . although the right one slides . . . the other is just a finger rest for setting the amount of brake you'll need.
With both our previous 2013 Heartland Trail Runner bumper pull trailer and our new Heartland Prowler 5th-wheeler, it seems that a setting of 5.5 is the perfect amount of brake.
To turn on the trailer towing feature, there is a button to push in on the tip of the shift lever at right of the steering wheel.