Hooray - someone wants to ead the instructions
You will find the manual, and some simple tutorials here:
http://audacityteam.org/manual-1.2/
Some bonus info that isn't in the manual:
iTunes often uses AAC for encoding the songs and this format is not compatible with Audacity. This gives you two choices, either:
1) Use a decoder to convert the tracks into wav format.
A suitable encoder is "SUPER"
http://www.erightsoft.com/SUPER.html
It has a slightly strange interface and it is a pain to download, but it's free and it works for loads of formats.
2) Play the track with your usual iTunes player and record it with Audacity by selecting "stereo mix" as the recording source in the Windows Mixer. ("stereo mix" may be called "What You Hear" or something else, depending on your sound card),
If your pre-recorded songs are on CD, you will want to use a "ripper" to extract them in wav format. An excellent free ripper is "Exact Audio Copy" and another one is C-Dex:
http://www.exactaudiocopy.de/
http://cdexos.sourceforge.net/
For burning to CD you will also need CD burning software. I'd recommend Nero - it's not free, but it's quite cheap, and on Windows it's my favourite. Make sure that you select "Audio CD" as the format if you want to be able to play it in a normal CD player.
This IS in the manual, but it is one of the most common problems on the forum:
When you "Save" in Audacity, it creates an Audacity Project File (.aup) and a folder containing data files. This is NOT normal audio. To get normal audio (for burning to CD or uploading to iTunes) you must "Export" the audio.
Note also that in v.1.2.x when you Export, all tracks are mixed down into a single file INCLUDING any muted tracks (they are not muted in the Export mix). This is slightly different in v.1.3.4 in that muted tracks stay muted in the Export mix).
Have fun.