Installing an LED tube light in an existing fluorescent fixture is relatively simple.  If the fixture has an electronic ballast, you need to remove that and then wire the power directly to the end sockets.  This is fairly simple, and typically you can use the existing wire in the fixture and then just add some wire nuts.  If you have an older fixture with a magnetic ballast and starter, you will have to remove or open the starter and remove or short the magnetic ballast. Remember, of course, that when servicing a fluorescent fixture or lamp for any reason, electrical power to the entire fixture should be disconnected. This is not always practical in situations where a large number of fixtures are controlled from the same power control (such as in open office areas). In these cases, insulating gloves and a nonmetallic ladder should be used if the fixtures must be serviced when power is present.

Below, are some diagrams and then some pictures I took of an actual installation in a fixture.

Wiring Diagram for Retrofit of Fixture with Electronic Ballast

Here is a picture of the actual electronic ballast that I removed from the fixture in this example.

Electronic Ballast with Wires Clipped

Depending on how much wire you have to work with, it is a good idea to leave long enough wires leading out of the ballast to be able to reconnect the ballast with wire nuts, if you should ever want to convert the fixture back to use for fluorescent bulbs or want to use the ballast somewhere else.  In this example, I have clipped the wires a little too close to the ballast, but then, I am not planning on ever using this ballast again.

Now, here is a picture of the wires connected with wire nuts.

Wires Connected with Wire Nuts

In the picture above, I have placed the electronic ballast with the clipped wires in the fixture so that you can see how it was wired previously, but you would, of course, remove the ballast from the fixture.

I don’t have any pictures right now of a retrofit to a fixture with a magnetic ballast and starter, but here is a simple wiring diagram.

Wiring Diagram for LED Retrofit to Fixture with Magnetic Ballast

So, that’s all there is to it.