APEX

Hi,

I have created a registration form for a sample application, and it's all working great, except for i dont know how to use the inputted data to add the new user into the
security system of the application. I'm using the standard apex authentication scheme. But it's just not clear in which table i have to insert the username and login to let them be
able to log in.
Any help would be much appreciate.

PS. if it was not obvious yet, i am an beginner in this :)

Thank you very much