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 flapper chain from the flush lever
Unhook the old flapper from the overflow tube pegs
Remove the old flapper
Install the new flapper onto the overflow tube pegs
Reconnect the flapper chain to the flush lever
Adjust the chain length so it has slight slack
Turn the water supply back on
Let the tank refill
Test the flush
Check for proper sealing and adjust if needed