Turn off the main breaker
Verify the power is off with a voltage tester
Remove the panel cover
Identify the faulty breaker
Note the breaker type and amperage
Disconnect the wire from the breaker
Release the breaker from the bus bar
Remove the old breaker
Install the new breaker in the same slot
Reconnect the wire securely
Snap the breaker onto the bus bar
Replace the panel cover
Turn on the main breaker
Turn on the new breaker
Test the circuit