Summarize this article in one sentence.
Generally, most basic computer microphones will have one of two varieties of jack: an 1/8" TRS jack, which is essentially the same kind of jack you would find on a pair of headphones, or a USB jack, which is flat. Both of these jacks have corresponding ports on most computers. If you're using an XLR microphone, a quarter-inch jack, or some other variety of mic, skip to the next section. Almost all desktop computers will have visible microphone ports on either the front or the back of the tower. Usually, this port will be colored pink, and have a microphone image over it. If you have an eighth-inch jack, all you've got to do is plug it into this port and start testing sound.  If you have a USB jack on the end of your microphone, most computers will have two or more USB ports on the side, or the back of the computer. Simply plug the USB jack into one of these ports. Laptops and some more contemporary computers don't have microphone ports, because they're generally outfitted with internal microphones. It's usually possible to plug into the headphone port on most computers, however, and adjust your sound settings later. The easiest and quickest way to test your levels and check your settings is to go to your input sound options and make sure that the device you just plugged in is visible, and that it is selected for use. Open a recording program and attempt to use the microphone and set the levels.  On Windows, you can use the Sound Recorder, on a Mac, Quicktime or GarageBand should do fine. If you're not getting a signal, skip to the last section for troubleshooting tips.
Examine the jack on the microphone. Locate the corresponding port on your computer. Test your new microphone with the recording software of your choice.