After registering you may login to your Joomla website allowing you specific access depending on your user group
1) Scroll down to the Login module, click the User Name field and enter your username
2) Next enter your password for your account
3) To stay logged in and not have to enter your username and password next time you visit this site, checkmark the Remember Me checkbox
4) Now click on the Log in button
That is it, now you know how to login to your Joomla website