The tutorial is a work in progress. It provides too much information to be a tutorial, and too little to be a reference.
For first time readers, simply ignore all DETAIL (they look like this NOTE, but grey) as they contain additional information on language design, unsolved problems and known bugs. If you wish to contribute, DETAIL is a good place to start. In the future all DETAIL would be moved to either Language Design or Contribution.
The recommended way to edit REAM files is to use REAM Editor, a web-based editor designed to read and write REAM files. It runs entirely in the browser and requires no local installation. A lite version of REAM Editor is embedded in this documentation for readers to test the examples.
You can also edit REAM files with any text editor, and use the standalone compiler to compile the datasets. See ream-core for installation guide.