Facebook group can be a great way to spread the knowledge that you are teaching with your online course.
In two ways
the one is by creating live events about your subject and educate people about the benefits and the needs that you course cover.
And by creating an open space where other creators can give their own ideas and knowledge about the topic.
This is bringing new ideas and knowledge exchange which finally will let people satisfied and ready do take advantage by involving more in all the products that you offer.
Become a member and add your online course here https://www.facebook.com/groups/1603532493125489