This whole thread is off-topic for the developers list. This list is for development of Mailman, not for teaching people to use it. Read the whole recommended documentation before you ask busy developers to tutor you in very basic things. There's a email@example.com list for users to help each other. All of the Mailman developers who might be willing to answer your questions are there as well, but there are also many experienced users, some of whom have experimented with the REST API who will also help. Please reply there for further help. (Reply-To is set.)
That said, there are plenty of URLs in the API documentation. Here's a hint: search for "dump_json". That function takes an URL. You may want https: instead of http: in your URLs, and you may need to change the port from 9001, depending on the configuration of your REST server. Try it with simple GET requests for information first, such as for domains or lists. You can also do these requests with an ordinary web browser, though I don't know what it will do with the JSON-formatted reply.
If you don't have domains and lists configured, I suppose the informational requests will come back as empty JSON objects. It should be safe to make them. You can either use Postorius to bootstrap a few example domains, lists, and users, or (the hard way) figure out how to POST appropriate requests. I don't recommend trying to update the backend DBMS by hand; the schema is quite complicated. I don't know how to use curl to update Mailman's databases. That requires a POST request which I have never done with curl. The POST request needs to be valid JSON.
The more I think about this, the less I think your idea of using curl is worthwhile, because formatting JSON requests by hand is going to be a real annoyance and a great way to mess up your database with spurious information. You're really going to want programmatic support for this. But that's already all available in Python in the Mailman system.
It's up to you, but I feel a responsibility to warn you that using curl is not going to be simpler than learning enough Python to do these things.