The tool in VS 2013 does not support adding this to an existing project. At the bottom of the link that you are referring to in the Additional Information section, there is a deep dive article in which I analyze the added code and configuration. Thus, you can use this as a link to search for deltas and apply them to your project.
Visual Studio 2015 now offers us some hope in this scenario. Of course, in the preview, but you can try. In Solution Explorer, right-click on an existing project and select the Configure Azure AD Authentication option.

Rick rainey
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