Audacity:
Audacity is free, open source software for recording and editing sounds. It works on both PCs and Mac computers. Typically, instructors will record audio through either a headset (with a microphone), or table top microphone that then goes to a mixer, and into the computer. You can buy a headset (with a microphone) for $20-$50. We use Logitech "Clearchat" products. You will get a better recording if you use a headset rather than a builtin microphone on your laptop computer.
LAME:
Free encoding software that works with Audacity. Install both so that you can export audio as MP3 files from Audacity (Audacity uses LAME to make the conversion to MP3).