The answer to 'how to install circuit breaker' is to first turn off the main power supply and identify the circuit you want to install the new breaker for. Next, remove the old breaker and install the new one, making sure the amperage rating matches the circuit. Connect the wires securely, then turn the power back on and test the new breaker to ensure it's working properly.
It's important to follow all safety precautions when working with electrical systems, including wearing rubber-soled shoes, using insulated tools, and turning off power at the main breaker before beginning work. If you're not comfortable working with electrical components, it's best to hire a licensed electrician to handle the installation.