You can only log in to the Administrator interface if you have administration or back-end privileges. The Administrator interface(application) can be reached by appending the word
administrator to the URL of your site. For example, if you usally access your web site on:
http://www.example.com/administratorto access the Administrator panel
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.