It seems that snippets of MVVM Light are not installed when we use Nuget to install MVVM Light Toolkit.
Where can I find them ?
For anyone else who didn't find C# snippets in the download specified in the accepted answer, you can download MVVM Light extension
This not only installs C# snippets for you, but also the relevant Project and Item templates.
The download works with the Community Edition of VS2015 too.