The answer to 'how to install junction box' is to first turn off the power to the area where you will be working. Then, locate the existing wiring and determine the appropriate size junction box needed. Carefully cut the drywall or plaster to expose the wall cavity, and use a stud finder to locate the nearest wall studs. Secure the junction box to the studs using screws, making sure it is level and flush with the wall surface. Connect the wires according to local electrical codes, using wire nuts to join the hot, neutral, and ground wires. Finally, replace the drywall or plaster and finish the area, ensuring the junction box is accessible.
Installing a junction box is a common electrical task, but it's important to take safety precautions and follow local codes. If you're not comfortable working with electricity, it's best to hire a licensed electrician to handle the job.