Configuration file is not writable
Configuration file permission settings
osTicket installer requires ability to write to the configuration file. A template copy of the file, settings.php, is located in the include directory (include/settings.php). Please follow the instructions below to give read and write access to the web server.
Shh/Telnet
chmod 777 include/settings.php
FTP
Using WS_FTP this would be right hand clicking on the file settings.php , selecting chmod, and then giving all permissions to the file.
Cpanel
Click on the file, select change permission, and then giving all permissions to the file.