Jack up and remove the wheel. Look inside the drum for a small metal nipple on the brake line. Unscrew this nipple to drain brake fluid and release pressure on the calipers. Take brake drum off to access pads and springs.
If it is just the brakes and not the rotors or calipers, etc. , you can do it by ordering the right brake pads first. You will need to use a jack to lift one rear wheel and remove the wheel and tire. After that remove the old brake assembly and take out the used pads, replacing them with new ones.
Raise and secure vehicle on jack stands. Remove wheels and set aside. Remove calipers, and attach to truck side rail using Mechanics wire. Remove inner and outer pads. Compress piston with C-Clamp
Reinstall calipers and Torque to 26 lb/ft
Reinstall wheels and bleed
Raise the rear of vehicle, secure with jackstands, remove wheel, unbolt caliper,slide out old pads. Install new pads, compress the brake piston, reattach the caliper and wheel.