A couple of good, similar posts about getting your Core Data database in iCloud for apps…
iOS How-To : Using Core Data with iCloud – Une goutte d’eau dans la mare du web.
http://timroadley.com/2012/04/03/core-data-in-icloud/
These steps/methods are pretty much cut-and-paste but require some Provisioning Portal steps, etc.
I had to remove the dispatch call…
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
… in Tim’s persistentStoreCoordinator method. It seemed to be a timing issue.