The instructions on the above website can sometimes be outdated. If you have any issues running a sample React Native application, please open an issue at https://github.com/TAGraves/production-ready-rn-codemash-2019/issues and I will try to help.
Available tool downloads for each platform:
An up to date version of NPM. This will get installed with Node. If you have a custom environment with different version, please make sure that NPM is up to date.
Node.js for your development platform: https://nodejs.org/en/download/