How do I install an electric light switch?

I want to add a light switch to a light in my basement. It currently uses a pull chain to turn on and off, but is on the other side of the room. I now that the wire that supplies power to the light runs through the ceiling. Can I use that? If I cut it, I will end up with (2) black, (2) white and (2) ground. Then what do I do?

If you're asking what to do with wires after you cut them, DON'T CUT THEM. CALL AN ELECTRICIAN!

For a light with one light switch and the light at the end of the line.

Turn off the power to the line first, then test to make sure it's off.
all white wires get wire nutted together.
All Copper/bare green ground wires get wire nutted together.
One black wire goes to one side of the switch
The other black wire goes to the other side of the switch.

All connections must be inside an approved electrical box with a matching cover.

All boxes must remain accessible - They can't be covered up by the drywall or anything else you have to tear out to access the wiring.

Kill the power to the light. If you can get to the box where the light is attached with a wire to the location where you want the switch will be best. Remove the light base, unscrew the BLACK wire from the base of light. With the NEW wire that you ran, wire nut the WHITE wire to the BLACK wire that you unscrewed from the light. The NEW wire BLACK now goes to the terminal on the light socket that you unscrewed in the previous step. At the switch location, your romex wire needs to go into a "switch box" mounted on the wall. Strip the wire ends and place one wire on each of the screws on the side of the new switch. Color doesn't matter. There will be a small screw that screws on the metal portion of the switch, this is for the ground wire. Sounds complicated, it is real easy.

1) Turn off the circuit breaker that controls the light fixture you want to add the switch for.

2) When you are sure the power is off, remove the light fixture so you can access the wires in the box that the fixture was hanging from.

3) Identify the size of wire in the box (14-2 or 12-2) and get the same type of wire from Lowe's or Home Depot for your switch.

4) Run the wire carefully from the location of the light fixture, to the location you want your switch to be. Make sure you keep it away from anything that could cut or burn the wire.

5) At the light, strip the sheathing off of the cable and put the wires in the box so that there is at least 1/4" of sheathing inside the box.

6) You should now have 2 blacks, 2 whites, and 2 ground wires in the box.

7) Twist your two ground wires together leaving about 6-8" of wire outside of the box.

8) Color the NEW white wire black. This can be done with a marker, or by using black electrical tape. This is done out of consideration for the next guy who has to get in this box, so it is immeadiatly identified as a HOT wire, not a NEUTRAL wire.

9) Strip the ends of the wire you colored black, and the existing black wire and twist them together with a wire nut, and neatly fold them into the box.

10) You now have a black, a white, and your grounds to attach to the fixture. Attach them and re-install the fixture.

11) Now, go over to where you ran the other end of the wire for your switch. Get the wire in a box that you can install a switch in, and strip the sheathing off of the end and put the wires in the box, just like you did at the light.

12) Color the white wire black again, and then you'll have 2 blacks and a ground for your switch.

13) Put a black wire on each HOT terminal of the single pole switch. And the ground on the green screw. Make sure all connections are tight.

14) Screw the switch into the box and put a cover plate on. Make sure your ground wire is not touching the hot terminals on the switch when you put the switch into the box.

15) Turn the power back on, and check your switch. That's it!