Help files
All the help files are bundled with the executable, however they are also available here for reference: in French, German, Japanese, Chinese (Simplified), Estonian and English.
Creating a plugin
Follow this link for a tutorial on how to create a plugin, or that one for the full Appetizer API Reference
Building Appetizer
Some information on how to build Appetizer: Building Appetizer with wxWidgets and Visual C++ Express Edition.