Start with a Google search for "os x basics tutorial" and you will turn up things to read that should get you started. Then based on what you read, do additional Google searches via your web browser (which I assume you have some understanding, as you were able to post to this forum 😁).
Here are some things I found to get you started
https://www.apple.com/support/macbasics/
http://www.gcflearnfree.org/osxbasics
http://www.macforbeginners.com/
There is a lot of information out there.
Also go to a bookstore. One with a nice coffee shop, and browse the Mac books, while having a nice beverage. If you find a book that speaks your language, consider buying it, or drinking lots and lots of coffee in the bookstore's cafe 🙂
Then go home, and experiment, then do more Google searches, and more visits to the bookstore, until you are ready to teach classes.
PS. The correct name is iMac. Mac is short for Macintosh, as in a macintosh apple. Macintosh is the parent name of Apple's desktop and laptop computer line. Mac for short. The i (lowercase eye) was first added back in the mid-90's to stand for an internet connected Macintosh. So you have an iMac.
PS to the PS. You should NOT put your email address anywhere in public forum, as there is software out there that scans public forums for email addresses to then us for sending SPAM (junk email far worse than what the U.S. Post Office puts in your mailbox outside your house).
In general do not post any personal information in a public forum. No phone numbers, no addresses, no dates of birth, no email addresses, no SSN's, nothing, nada, nyet!