Are you talking about the admin panel for DewNewPHPLInks or something else ?

If you installation is viewable at /links/directory/ then the DewNewPHPLinks admin panel should be viewable at /links/admin/

On Apache webservers you would normally find a .htaccess file in a password protected directory. Possible your FTP program doesn't show you files that start with periods? They are system files after all and it's common to hide them.

Once you locate the file, renaming it would remove the password protection. Presumably your web host has some kind of control panel feature that would allow you to password protect it again. For that matter it may simply allow you to change the current password without renaming the .htaccess file at all.