You won't get any help from the iTunes App Store, it has no connection with Android at all. Smoothsync should be able to access your account simply with the account name and password (as long as you haven't set up 2-step authentication); there is a Help page accessible from the settings within the app. Also the Play Store page says:
Important note for Android 4.1 and Samsung users: To prevent the removal of your accounts on reboot install this app (before you install SmoothSync):
https://play.google.com/store/apps/details?id=org.dmfs.jb.workaround.icloudcalen dar
Please note that there is a new issue in Android 4.4: http://code.google.com/p/android/issues/detail?id=66905
It causes accounts to be removed when an app is updated. Installing the workaround app should help.