I recorded a quick getting started video for this Microsoft GitHub sample.   Walks through all the steps and even shows the SQL Local DB storage and how to verify security with Fiddler Composer sending test HTTP traffic. 

This pattern is a great way to enhance Officer 365 SharePoint team sites with advanced functionality.   Host AngularJS single page application (SPA) on the front end along with an Azure AD secured WebAPI backend.   Lots of potential for replacing traditional WSP farm solutions with new cloud development patterns.

Enjoy! 

Source Code

https://github.com/Azure-Samples/active-directory-angularjs-singlepageapp-dotnet-webapi

Video