To download and install the latest version of Audacity (2.3.2), go to this page and follow the instructions (picking either Windows or Mac depending on your computer): https://www.audacityteam.org/download/
Don’t forget to download the FFmpeg plug-in (video for Mac users here)
After you have Audacity up and running on your computer, make sure you also download the optional plug-in FFmpeg, which “allows Audacity to import and export many additional audio formats such as AC3, AMR(NB), M4A and WMA, and to import audio from video files.” Note that the 64-bit version is required for Audacity 2.3.1 and above. To download FFmpeg for Mac, follow the instructions here. To download FFmpeg for Windows/PC, follow the instructions here. If Audacity was open while you downloaded FFmpeg to the default location, it should automatically locate the library. To check, in Audacity click on “Preferences” under the Edit tab, then select Libraries, and see if the FFmpeg shows three numbers for “F,” “C,” and “U.” If not, you can locate the library manually using the instructions on the pages linked above.