Web services

Hello, the documentation you are talking is about implementing functions to be used with xmlrpc, but how can I use these functions?

Now I'm trying to enrol a user to a course. I have Moodle 1.9.4+ and an external application that manages users.
I need to manage moodle from this app. Enrol users, Asign roles...

How can I enrol an user to a course using web services? Any tutorial or documentation?

Thank you.

P.S. I'm new in Moodle, I hope this questions are not very stupid