Electricity can be dangerous, so it's important you ensure wiring is connected safely. Different appliances require different size wires, depending on the wattage the appliance needs to operate. Light bulbs are generally low wattage, usually between 25 and 75 watts, so using a reasonably thin gauge wire, such as AWG 16 to wire a lamp holder, is fine.
Check the light bulb fitting on the lamp holder to ascertain if it needs to have a ground wire. Unscrew the light bulb unit from the lamp holder using your hands to access the terminals. If it has three terminals, then you need to use tri-core wire, but if it has two terminals, then dual-core wire is needed.
Remove about 2.5 cm (1 inch) of outer plastic from the wire using wire strippers so you see the internal coloured wires. One is brown and the other blue. If you are using tri-core wire the third wire is green or green and yellow striped.
Remove 6 mm (1/4 inch) from the end of the internal wires using wire strippers. This reveals the copper metal core that connects to the lamp holder terminals.
Find how to access the inside of the lamp holder so you can feed in the wire. This is usually done from the base of the unit or side. All lamp holders are different, so you need to work out the method appropriate for yours. You probably need to undo the base or side plate using a screwdriver.
Slide the wire into the lamp holder until it protrudes where the light bulb fitting goes. Pull enough out so you can easily connect the wires to the light bulb fitting.
Loosen the two or three terminal screws on the light bulb holder using a screwdriver. Just loosen them enough so you can insert the copper wire into the terminal holes.
Insert the blue wire into the terminal labelled "-" or "neg" then tighten the screw using the screwdriver. Insert the brown wire into the terminal labelled "+" or "pos" and tighten the screw. If you have a third wire connect it to the terminal labelled "gnd" or "t" and tighten the screw. Be sure the connections are secure.
Put the light bulb fitting onto the lamp holder. You need to slide the wire inside the lamp holder. It may be easier to pull the opposite end of the wire to help the process. Screw the light bulb fitting onto the lamp holder using your hands.
Replace the base or side plate and hold it in place by tightening the screws using a screwdriver as necessary. Put a light bulb into the light bulb holder. It either screws in place or you need to push gently down and twist the bulb using your hand, depending on the type of connection and type of bulb.
Insert the plug on the end of the wire from the lamp holder into the power socket. Turn on the power to check if your lamp holder is working.
Use wire that has a pre-fitted plug on one end. It is readily available from electrical shops and makes the task simpler.