The admin password is set up during installation. It is not stored on the website – only a 'salted and hashed' version is stored.
If your browser has cookies enabled, the site administration 'admin' password does not need to be entered each time an admin page is opened.
Lost or forgotten admin password
If you have lost or forgotten your admin password, you can't recover it from the website. It isn't there. Upload install.php to the 'admin' folder and go through the installation procedure again. You will also need to salt and hash the password again.
Note: you will not lose the content you have created on your website.
Public pages are password-protected individually, each with its own password. When creating a password-protected page enter:
... on the first line. It will need to be re-entered each time the page is viewed.