I do not see how to paste the web link in order to import audio from a youtube video. I have done it before but cannot remember how I went about it.
Google “Import YouTube Audio.”
You can [u]record streaming audio[/u] with Audacity.
Or, there are various utilities for downloading the audio/video. (YouTube tries to prevent you from doing this and it may be a copyright violation depending on the content.)
Once you have downloaded the audio/video file you can open-import the audio with Audacity. Depending on the format you’ll probably need the optional Audacity FFmpeg library to open it.