If you are interested in using the GOV.UK Prototype Kit it is openly available and highly recommended as a fast way to build prototypes. Note: that is not for production code.
Do be aware however that at the moment not everything is ‘plain sailing’:
What can happen is that you download the current latest version of Node.js and find yourself running version:16. However, this version is incompatible with the current GOV.UK Prototype Kit version 9. That requires Node.js version 12 LTS.
What you will need to do is to uninstall v16 and this time make sure you download and install the latest of Node.js 14 ensuring of course you pick the right installation file for your operating system.
Instead of pointing to https://nodejs.org/en/ it would be far better to be specific in the instruction and instead point users to https://nodejs.org/download/release/latest-v14.x/ at least until the GOV.UK Prototype Kit is compatible with the latest version, hopefully in the release of version 10 of the kit.