Turn off the water supply to the toilet
Flush the toilet to empty the tank
Remove the tank lid and set it aside
Disconnect the old flapper from the flush chain
Unhook the old flapper from the overflow tube pegs
Take the old flapper to match the replacement size if needed
Attach the new flapper to the overflow tube pegs
Connect the flush chain to the new flapper
Adjust the chain so it has slight slack
Turn the water supply back on
Let the tank refill
Test the flush
Check for proper sealing and adjust the chain if needed