Log in, and use 'sudo -s' to give you a root shell, but with your account password. Also, you can give yourself permission by using 'su'.
Did you have to set a root password when you setup the account? A lot of GUI login managers will disallow root access, but you can change it to allow it. In KDE there is a whole section for the login manager, and enable it to allow root. Of course, it's not a good practice to log into X as root at all.
If you did set a root password, you can run the GUI tool with the 'kdesu' command, and it will authenticate before it starts it.