Thank you for your comment.
Your method will just fill the site with some random users and data, which I do not want. And I do not want a staged online site, I can just host it locally if I want.
This is for a production environment. Dummy users will actually have some meaningful topics. The purpose of this is not to present an empty site to the public.
So, kindly let me know of a solution related to the question I mentioned.
I just need to insert users (I have the name list for the users), into the main DB of discourse.
Thank you.