Okay perfect. Using the file path defined in config.php by $pass_file add one line using the following format:
username:hashed_password
In order to get the hashed password copy the following code into a file named test.php and navigate to it:
echo base64_encode(sha1('PASSWORD'));
?>
Replace PASSWORD with whatever you want to login with.
As a side note I suspect the directory housing your files is not writable by PHP or your server’s php.ini is preventing file operations.
Hope that helps!