Error to download npm package in Visual studio 2015 when you are in corporate proxy

This is the command to run to set up the proxy,

npm config set proxy http://proxy.company.com:8080
npm config set https-proxy http://proxy.company.com:8080

But where to run this command, the npm.cmd is in,
C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\Web Tools\External

Open a command prompt as administrator and run the npm config ...
Then it worked.