To replace a car's rear drum brakes, start by jacking the car up so that you can remove the rear wheel and tire. Remove the brake drum that is attached to the wheel, and wash it with soap and water.
Check whether you can remove the brake assembly by simply popping the brake shoes over their brackets. If this isn't possible, use a pair of pliers to press the spring on one of the pins located on either of the brake shoes. Rotate the pin with your hand until the round clip releases. The pin should slide out the back. Do the same for the rest of the pins on the brake shoe and the pins on the other brake shoe.
Put together the parts of the new brake shoe assembly, being careful to attach the springs to the right positions. You may reuse parts from the old brake assembly. Place the brake shoes over the brackets at the bottom of the brake assembly, and then place them at the top. Next, replace the spring-loaded pins that hold the assembly onto the backing plate.
Reattach the brake drum onto the front of the backing plate. Reassemble the wheel bearing, and put back the tire. You may drain the old brake fluid and pour in new fluid.