If you know how to adjust a drum brake, its exactly the same. The ebrake is actually drum brakes on the rear axle.
Look on the back side of the brake, below the axle. Theres a little rubber piece. Pull that out, theres a spindle in there you need to turn with a flathead screwdriver. You have to pry the spindle up. Jack the tire up & turn the spindle till the tire won't turn. Then back off 5 or so turns.
If this doesn't help you'll have to pull the rotor/drum off and replace the shoes.