The Administrator back-end of your Joomla! installation is where you do most of the work to set up, configure and maintain your website. As such it must be protected from access by casual visitors and so Joomla! will request a valid username and password before access to the Administrator is granted.
You access the Administrator back-end of your website by entering a special URL into the address bar of your web browser. If your website URL is http://www.example.com then you will enter the address http://www.example.com/administrator. You will be shown the Administrator login form which looks like this:
Enter your username and password into the relevant fields. If required, select your preferred language from the drop-down list. Then click the Login button. If you are logged in successfully you should see the Administrator control panel screen which looks similar to this:
To log out of the Administrator back-end, locate the Logout link in the top-right corner of the Administrator screens and click on it. Logging out will return you to the Administrator login screen. If the Logout link is greyed out and nothing happens when you click on it, then you are probably in a screen where you have some resource locked for your exclusive use. Click the Cancel toolbar button first to release the resource, then click on the Logout link.