Thanks Susan, and thanks to everyone else that responded. I seem to have finally figured it out through combination of you suggestions, searching the web, watching YouTube videos and good old trial and error. I have been able to move my locally created Quizzes into Canvas commons and added persons outside of my organization to be able to preview and edit the content. This was my original goal.
To be honest, I'm not sure which of my actions actually accomplished this. I managed to create a course and then exported my Quizzes as ZIP files, and first tried importing them into the course as a plain ZIP file. All that seemed to do was dump the files into a folder.
I then tried importing the file as a QTI ZIP. Eventually, after a few more false moves, I found the quizzes under "Quizzes" apparently all ready to go.
I was then able to add other users as Teachers from outside our organization and send them the invite. Once they accepted and created an account they were able to access them fully.
I think part of my confusion was the difference in functionality and appearance between my local account and the Instructure Commons one. I was also unsure if I needed to create a separate account to use the "Free for Teachers" and whether this was the same as a Commons account, etc., etc. I see that I'm not the only one who has been uncertain about some of this. One of the first discussions I came across was https://community.canvaslms.com/thread/13059-how-do-i-actually-use-free-for-teachers which still didn't help to clear things up for me.
In any event, I accomplished my goal thanks in a large part to the help given here!
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.