Hello @janecarmel
Some institutions will allow non-students or members have access to a course and you can add people not affiliated with the institution still technically. However, that largely depends on the institution and their procedures - you'd want to speak with them as it is an option. If you need to create a FFT account and course you can follow this guide:
How do I sign up for a new Free-for-Teacher Canvas... - Instructure Community
You can add users a course you make regardless of their affiliation with the institution. You can allow self sign up as well and if you need to make it completely public, Canvas Support can do that for you but you need to contact them directly and ask.
How do I contact Canvas Support? - Instructure Community