When all the other parts of your computer system are connected, you can then connect your system unit to a power source. Just make sure the power source is turned off before you connect!
Connect one end of the power cable to the cable connector on the back of your system unit.
Connect the other end of the power cable to a power source.
TIP
Use a Surge Suppressor
For extra protection, connect the power cable on your system unit to a surge suppressor rather than directly into an electrical outlet. This will protect your PC from power-line surges that could damage its delicate internal parts.