I have been a musician forever but this is the first time i’ve ever tried to record myself. I’ve downloaded and installed the software and now. pardon my ignorance, i’m not even sure where to plug my instrument into the computer. Any help?
First you need a soundcard that has a “Line in” (not to be confused with a “microphone in”)
If you are on a desktop PC then you probably have one - the socket will probably be one of a group of 3 or more mini-jack sockets on the back of your computer. You can plug something like an electric guitar directly into that (with a 1/4" jack to mini-jack adaptor), although it is much better if you can get a small mixing desk, and plug the main output of that into the line-in - you can then plug a variety of instruments or microphones into the mixer and record them with Audacity.
For getting started with Audacity, you may find it easy (and cheap) to just have a go recording from a computer microphone plugged into the “mic-in” socket. The sound quality will probably not be very good, but it’s an easy way to get started. Then have a go at some of the tutorials here: http://audacityteam.org/help/tutorials