Turn off the main breaker
Verify the panel is de-energized with a voltage tester
Remove the panel cover
Identify the breaker to replace
Disconnect the wire from the breaker
Release the breaker from the bus bar
Remove the old breaker
Install the new breaker in the same position
Reconnect the wire securely
Snap the breaker fully into place
Reinstall the panel cover
Turn the main breaker back on
Turn on the new breaker
Test the circuit
If unsure, contact a licensed electrician