It is interesting to note that most users simply ignored the question. Could it be that it is considered unnecessary to call on other libraries in conjunction with the Fusion 360 API? I find that in my own work, it makes some things easier for me to use numpy, matplotlib and some other modules. Please note that the experience here only applies to Windows 10.
From Anaconda, you can easily request a terminal from which your Python interpreter is reachable. In the Python version installed into Fusion 360, things are different. The real problem is to locate where the Fusion 360 embedded Python interpreter is located. Searching manually on my computer, I found it at:
c:\Users\myUserID\AppData\Local\Autodesk\Webdeploy\Production\abxy234...
That last subdirectory appears to be a 40 character random generate alphanumeric.
My initial fear stems from the fact that that last directory appears to change frequently and I therefore wonder if changes made will be permanent. I have tried it and so far, it works.
Once you move to that directory when launching
pip install numpy
or any other desired library, it works with the Python interpreter in Fusion 360.