Turn off the main power supply
Verify the power is off with a voltage tester
Remove the panel cover screws
Take a photo of the breaker and wire positions
Loosen the breaker terminal screw
Disconnect the wire from the breaker
Unclip or pull the breaker out of the panel
Match the replacement breaker to the panel type and rating
Snap the new breaker into place
Reconnect the wire to the new breaker
Tighten the terminal screw securely
Reinstall the panel cover
Turn the main power back on
Turn on the new breaker
Test the circuit for proper operation