To install the LAME and FFmpeg libraries for Audacity, follow these steps.
First, download Audacity from SourceForge, and install it.
Next, run it, and go to Edit > Preferences, then click Libraries.
You can click either download button, you will be taken to this webpage. Then, follow the links to download the LAME library and FFmpeg.
To verify correct installation, go back to Audacity’s Edit > Preferences, Library pane, and verify version numbers are displayed, as below: