Step 1. Go to the FFMPEG library download page: https://lame.buanzo.org/#lamewindl
Step 2. To Install FFmpeg for Windows, scroll down to “TO DOWNLOAD Lame and FFmpeg for Windows", left-click on “ffmpeg installer download ” to download the latest version of FFMPEG; we use Windows as an example to explain the process here. Mac and Liunx users can apply the similar steps.
Step 3. After downloading the .exe file, find it on your computer, double click to run the installer.
Step 4. Hit Yes > OK > Next >Next, and specify the destination as C:\Program Files\FFmpeg for Audacity or C:\Program Files (x86)\FFmpeg for Audacity for Windows 64 bit version.
Step 5. Click Next > Yes > Install. Now you have finished the installation. Please remember to restart Audacity.

You can also manually check and install FFmpeg library in Audacity.
Step 1. Launch Audacity, go to Edit > Preferences.
Step 2. On the Preferences dialog, select Libraries > FFmpeg Library: Locate.
Step 3. If you have successfully installed FFmpeg library, a success dialog pops up.
Step 4. If not, you will see a Locate FFmpeg dialog. Click Browse, head to the folder containing FFmpeg and select avformat-55.dll.
Step 5. Click Open > OK > OK.
