Turn off the water supply valve on the wall behind the toilet.
Remove the lid from the toilet and place it on a solid surface, out of your way.
Flush the toilet to remove the water from the upper tank. If the handle is broken, lift the flapper and hold it up until the water drains from the tank.
Unclip the chain from the end of the flush arm.
Loosen and remove the nut on the inside of the tank, securing the handle to the tank.
Pull the handle and flush arm through the handle hole and remove.
Remove the flapper from the tank by unclipping the ears on the back of the flapper.
Clip the ears of the new flapper onto the stem and lower the flapper onto the valve.
Install the new flush arm through the handle hole on the front of the tank. Place the nut over the flush arm and thread it onto the inside of the handle to secure both the handle and flush arm to the tank. Do not over-tighten the nut.
Clip the chain from the new flapper onto the flush arm.
Turn the water supply valve back on and allow the tank to fill completely.
Flush the toilet and adjust the chain if too much slack is provided.
Replace the toilet lid.