Update flat-bundles.md (#1600)

* Update flat-bundles.md

Added additional information on deploying a flat bundle

* Edited the change request

Author: andyliumsa

windows-apps-src/packaging/flat-bundles.md

@@ -37,4 +37,12 @@ For more information on using MakeAppx.exe, see [Create an app package with the
 Alternatively, you can create a flat bundle using the packing layout. To do this, set the **FlatBundle** attribute to **true** in the **PackageFamily** element of your app bundle manifest. To learn more about the packaging layout, see [Package creation with the packaging layout](packaging-layout.md).
 
 ## How to deploy a flat bundle 
-Before a flat bundle can be deployed, each of the app packages (in addition to the app bundle) will need to be signed with the same certificate. This is because all of the app package files (.appx/.msix) are now independent files and are not contained within the app bundle (.appxbundle/.msixbundle) file anymore. Once the packages are signed, use the [Add-AppxPackage cmdlet](https://docs.microsoft.com/powershell/module/appx/add-appxpackage?view=win10-ps) in PowerShell to point to the app bundle file and deploy the app (assuming app packages are where the app bundle expects them to be). 
+Before a flat bundle can be deployed, each of the app packages (in addition to the app bundle) must be signed with the same certificate. This is because all of the app package files (.appx/.msix) are now independent files and are no longer contained within the app bundle (.appxbundle/.msixbundle) file. 
+
+After the packages are signed, you can install the app via one of these options:
+* Double click the app bundle file to install with App Installer.
+* Use the [Add-AppxPackage cmdlet](https://docs.microsoft.com/powershell/module/appx/add-appxpackage?view=win10-ps) in PowerShell and point to the app bundle file (assuming app packages are where the app bundle expects them to be). 
+
+You cannot deploy the individual .appx/.msix packages of a flat bundle by themselves. They must be deployed through the .appxbundle/.msixbundle. However, you can update individual .appx/.msix packages of a flat bundle after the initial install. 
+
+For example, if your v1 flat bundle is composed of an .msixbundle, an x86 .msix, an x64 .msix, and an asset .msix, and you know that your v2 bundle only has changes to the asset package, then you only need to build the .msixbundle and the asset .msix to be able to install the update. You must build the .msixbundle for v2 because the bundle keeps track of all the versions of its .msix packages. By bumping the version of the asset .msix to v2, you need a new .msixbundle that has this new reference. The v2 .msixbundle can contain references to the v1 x86 .msix and x64 .msix; the .msix packages of a flat bundle does not need to have the same version number.