In order to be able to manage your projects' packages, you need the NuGet Package Manager. This is a Visual Studio Extension, explained in the official docs: Installing and Updating NuGet Client.
Starting with Visual Studio 2012, NuGet is included in every edition, and can be used from: Tools -> NuGet Package Manager -> Package Manager Console.
You do so through the Tools menu of Visual Studio, clicking Extensions and Updates:
This installs both the GUI:
And the Package Manager Console: