Installing the Power BI dev tools looks pretty straight forward. However as most of us are probably behind a proxy server you might come across this annoying failure.
npm install -g powerbi-visuals-tools npm ERR! Cannot read property 'path' of null
You have to look in the log file for an error message that actually shows the 407 http error.
Basically configure npm to use the http registry address instead of https and pass in the proxy address and windows login in the call.
npm config set strict-ssl false
npm config set registry 'http://registry.npmjs.org'
npm --proxy http://username:password@myproxyaddress install -g powerbi-visuals-tools