What do I do if my package isn't being detected?

Question

I am on Windows. If I run a piece of Python code including import manim, the following error message appears.

RuntimeWarning: Couldn't find ffmpeg or avconv - defaulting to ffmpeg, but may not work warn("Couldn't find ffmpeg or avconv - defaulting to ffmpeg, but may not work", RuntimeWarning)

However, I have installed ffmpeg via pip. What should I do?