As the documentation itself explains you should use the
npm install -g @angular/cli
To access the command line tool that creates and manages angled projects. The reason for not working is that with the -g
flag it indicates that you are installing the NPM package in global mode, that is, you will be able to use it by running ng [options]
after running the installation. Without the flag you are installing the angle cli in your current folder and not the angle itself.
Follow the initial tutorial on Angular 2 to learn how to use the framework correctly.
Source: link