You simply copy the package and all the dependencies in your folder node_modulesinside the project for local installation or in the global folder ( npm config get prefixto see where it is located) for global installation.
The behavior npm installis to check the dependencies and install them first. When he does not find them installed or the local file containing them, he tries to download them.
Since all these steps do not work (you do not have the installed dependency, it is not available at the expected location and cannot download it), the installation fails.
You can find the list of dependencies in package.jsoneach module, but since it is recursive, it may take a long time for everything to be correct, if you do it manually, npm does it by recursion.
npm install angular-cli, .