You directory tree for you apps under development will be:
C:\Users\<user name>\AppData\Local\Packages\<app package>
You probably know your user name so we are good there, but what about the app package? In your Visual Studio project open up the package.appxmanifest file. Visual Studio provides a nice editor that sits over the top of the pretty complex XML file. You want to head over to the Packaging tab  and looking for Package family name . You’ll want to copy that Package family name since that’s what you’ll be using to complete your directory path.
So for me the completed directory name looked like this.