The builtin Iguana Files repository contains example channels that demonstrate working with files. This includes things like: parsing CSV files, loading and saving files, reading a directory, etc.
Simply import the channels that you are interested in, review the comments in the code, and read the corresponding article in this section of the documentation.
You can also view the repository on GitHub: https://github.com/interfaceware/iguana-file.
Be sure to come back and review this section as we will continue to add examples when new modules are developed.