Hi Bill,
If you find yourself needing to install lots of external libraries and dependencies, you might find it more practical to install your own version of Python (Anaconda is a very good scientifically-oriented one Free Download | Anaconda) and install PsychoPy into that (i.e. PsychoPy itself just becomes another Python module, rather than being a stand-alone application that contains its own complete Python distribution).
Then PsychoPy will have access to other libraries with a simple import statement.
Anaconda makes it very easy to switch between multiple environments (e.g. you can simultaneously have Python 2 and 3 installed). It also has a very good package manager called conda. Anaconda comes with a lot of those scientific packages already, but if not, it could be installed from the terminal with a simple command like this:
conda install scikit-image
This would also install any needed dependencies for you, taking account of what you already have installed. Then that library would be immediately available to your PsychoPy scripts with a simple import