I don't believe there is a time limit for each training or number of people, but I think you should have at least 5 participants (just my opinion). You should start with a pre-training survey, create an agenda, create your content, Get feedback during your delivery and adjust your training as needed based on your participant's responses and knowledge, do a post-training survey.
You could offer to do some online trainings as well as in person. Here is a link
to the Certified Trainer Course. Let me know if you need additional help.