The octal permissions mentioned above are good if you're running the system on a UNIX OS, regardless of what system you are connecting from locally. It sounds like the op is running osticket on Windows, in which case flagging the settings.php file as 'Read-only' will address the issue.
From the OSTicket installation root folder
- open the ./include folder
- right click on the file settings.php and select 'Properties'
- under 'Attributes' click the 'Read-only' checkbox'
- hit OK
You should be all set