audacity
Downloading, installing and setup
Download and install Audacity
http://audacity.sourceforge.net/download/
While the software makers allow users to download the latest "beta" versions of the program, doing so may have some unexpected consequences. Generally "beta" software is still in a testing mode and could be unstable. If working on production material, it is suggested that users download the stable versions until the beta versions replace them.
This tutorial was written using the latest beta version, however, to keep it as up to date as possible.
Download and install MP3 encoder
While the MP3 encoder is listed as an optional download, it is required in order to export MP3 files. MP3 files are ubiquitous on the Web, and their small size with relatively low quality loss ensures that it will be quick and easy to download. Installing an MP3 encoder is highly recommended. The MP3 encode Audacity uses is called LAME.
Despite its name, LAME is a ubiquitous, open-source MP3 encoder that allows many software applications to create MP3s from uncompressed audio files. LAME is a reverse acronym for LAME ain't an MP3 encoder, which is deceptive because it is an MP3 encoder. The name was a reference to the early version of the software.
From the downloads page on Audacity's Web site, you will see some "optional" downloads. Click on the link for the LAME MP3 encoder, or follow this link: LAME MP3 Encoder.
Follow the instructions for downloading the LAME MP3 Encoder package to your computer. Once you have extracted the package, open Audacity, and select Preferences under the Audacity menu (Mac) or Edit menu (PC).

From the left menu, click on Import/Export (might be labeled differently in earlier versions of Audacity) then click on the Find Library button. If you didn't download the LAME library yet, there is also a download button to do this here as well.

Use the Browse... button to find the location of the LAME package file, either libmp3lame.dylib (Mac) or lame_enc.dll (PC).
Click OK.

