This page hosts the Visual Studio extensions needed to develop NM products on Windows.
Launch Visual Studio and open the options dialog (Tools → Options). In there, navigate to the Extensions & Updates which is located under Environment.
Create a new gallery and enter the following:
Now go to Tools → Extensions & Updates and you should have a new gallery in there called NM Extensions under the Online header. From there you can now install and keep the extensions up-to-date just like any other extension.