The import method works only once you've moved the application packages to the new datastore location used by the new instance of App Volumes Manager.
You can copy the packages from one location to another using WinSCP or SSH from the ESXi hosts. There's documentation on how to do this from VMWare and blogs somewhere out there on the world wide internet.
The following below worked for me, because each "machine manager" instance (vCenter) had access to a central storage where an app volume datastore already existed.
Old version 4, 2006
New version 4, 2303
On each version, add the relevant machine managers. I'm not sure if it matters if the machine managers (vCenter) are on the same domain or not. Once they're registered, on the NEW manager, go to storage and edit the datastore location to match that of the OLD manager (the one with your current app stacks). Then click rescan. It should, if I remember correctly, automatically start to populate the inventory, but if it doesn't, this is when you go in and "import" using the import function.
Go to Configuration > Machine Managers > click "Register Machine Manager" and add the second (or even the same) vCenter instance.
Not sure how "official" this method is, but it worked for me. Also, there is the risk in "importing" the older packages that they get updated to the current versions of App Volume 4, 2303 as in my case, but so far, I haven't seen any problems.
