For Windows 10, in the Start menu, search for "system environment", click on "Edit the system environment variables", click on "Environment Variables…", add a user variable that links to the .exe that you downloaded, and now you can call it from the command terminal. It usually downloads the video into the same folder as the .exe
Also you probably have to download an executable of FFMPEG that's linked as path variable too
Use the "-x" flag for extracting audio. The default format is .ogg, but you can also specify mp3 with "–audio-format mp3" after that.
More documentation here: https://github.com/ytdl-org/youtube-dl/blob/master/README.md