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 lever chain
Unhook the old flapper from the overflow tube pegs
Take the old flapper to match the size and style
Attach the new flapper to the overflow tube pegs
Connect the chain to the flush lever
Leave a small amount of slack in the chain
Turn the water supply back on
Let the tank fill
Test the flush
Adjust the chain if needed