Update README.md

README.md

@@ -25,7 +25,8 @@ Photo Editor primarily demonstrates:
 
 This sample requires:
 - [Visual Studio 2017 and the latest version of the Windows 10 SDK (10.0.17134.0)](http://go.microsoft.com/fwlink/?LinkID=280676). You can use the free Visual Studio Community Edition to build and run Windows Universal Platform (UWP) apps. 
-- Download and install the [C++/WinRT Visual Studio Extension](https://aka.ms/cppwinrt/vsix). 
+- Download and install the [C++/WinRT Visual Studio Extension](https://aka.ms/cppwinrt/vsix).
+- You'll need to have a collection of images available in your local **Pictures** folder. If there are no images or photos available at that location, the app will not show anything but the background when you run it.  
 
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