Audacity needs a LAME encoder file to save audio to MP3 format. Here is the step-by-step guide on the one-time download.
1. Open up Audacity
2. Click on Edit > Preferences.
Keyboard shortcut: Alt+E followed by F
3. A window will pop up. Select Libraries and then click on the Download button beside LAME MP3 Library.
A browser will pop-up.
4. Click on LAME Installation Section of the appropriate operating system. It will bring you to a new page.
5. Scroll down to the Installing LAME on Windows section and click on the external download page.
Note: If you have restrictions on downloading files, use the ZIP file option.
6. You will be brought to the external download page. Select the recommended installer package, be it Windows, Mac or Linux.
7. Click on the link "Lame_v3.99.3 for Windows.exe"
8. A pop-up appears. Click on the "Save File" button.
9. Check your downloads folder. Click on the Lame_v3.99.3_for_Windows.exe file.
Your computer may prompt you to allow changes to be made to it. Allow it.
10. The LAME setup wizard appears. Click through it.
11. Select where you wish to store the LAME file. Remember to copy this location. You will need it shortly.
12. Complete the setup wizard then click Finish.
13. Go back to Audacity Preferences screen.
13. Click on the Locate button beside MP3 Library. Paste the copied location here.
14. Click on OK when done. You should now be able to save your audio files as MP3s!