SAFETY FIRST: Protective gloves and eyewear are recommended at this point.
The rear brake pedal can be adjusted up and down by using a 12 mm wrench to loosen the locknut and turning the adjuster nut with a 10 mm wrench either counter-clockwise or clock-wise depending on where you want to position the rear brake lever. After adjustment, tighten the lock nut securely.
After adjusting the brake lever make sure the brake light works when the brake lever is compressed.