ZipApp does not create Appx file

ZipApp does not create an Appx file that can be loaded into the Store.  The website says "Use the control to upload the packages (the .appxupload file) that you created with Create App Packages in Visual Studio" but there is no clue in VS as to where to do this :-(
The VS help talks about Team Foundation Server, but I only have VS Express and can't find the UI anywhere - was expecting to see it under "Build" but it must be hidden away somewhere.....  Any ideas?