From FCKeditor Docs

CKFinder configuration in the PHP language is based on editing the config.php file. To learn more go throughout the following sections:

• Quick Start
• Sessions
• Access Control
• Images
  • Thumbnails
  • Scaling
• Resource Types
  • Built-in resource types
  • Adding new resource types
• Security
  • Double file extensions
  • Image Uploads
  • Html extensions
• File system Encoding