The keys to success are precise measurements so that you purchase the right sized replacement flange and extra attention to ensure that the toilet sits flush on the floor at the end of the project.
How to replace toilet floor flange.
To replace a toilet flange lay newspaper down on the floor around the toilet and turn off the water to the toilet before flushing and siphoning all of the water out of the bowl.
Rest the toilet bowl on its side place it on a towel or cloth to protect the floor and attach the replacement wax ring to the bottom of the bowl this technique helps ensure the ring is in the proper position when placing the toilet over the flange.
Lay the toilet on its side and put the new wax ring on the round mouth that sits on top of the flange.
Make sure to keep the toilet straight and as perpendicular as possible when lowering.
Next install a new wax ring.
Replace the nuts on the bolts.
Replace the toilet by lining up the holes on the toilet base with the two bolts.
If the toilet rocks because the flange is no longer.
Press down to seal the wax ring with the flange.