According the Gojko, the documentation is intended not so much as a FitNesse "first step", but rather as a quick reference for people familiar with FitNesse, and he hopes for the reference to be grown collaboratively by the community of users.
This first cut contains some useful agile acceptance testing thoughts, and information on using the fixtures from both the Fit and FitLibrary packages:
For each fixture type, this document explains the table format and fixture class structure and provides advice when to use and when not to use it. Each example is accompanied by the source code for Java and .NET FIT implementations, in a form that can be easily copied and used as a template for similar fixtures.The new gallery information can be accessed via a print-ready PDF, an executable FitNesse wiki, or a live web site.
For more by Gojko, be sure to check out InfoQ news on using FitNesse with .NET and DBFit for testing database code.
Two other classic resources are always Ward Cunningham and Rick Mudgridge's definitive book on Fit and the FitNesse user guide wiki at the tool's home site.