The best source of documentation is available at tomviz.readthedocs.io, it is developed on GitHub and will be kept up to date with the application. We published a tutorial on the visualization of volumetric data using Tomviz in Microscopy Today, and have made a basic user guide available as a downloadable PDF, along with a video tutorial shown below and on the main page of Tomviz in use. We also use GitHub issues to discuss bugs, feature requests, and ask questions. There is a tag on the Kitware blog dedicated to Tomviz updates too.