In order to use the sync feature, please follow the steps:
- Select the device you want to be the "Master" for the initial setup. This the device which shows and watch state will be applied to all other devices when iCloud is first enabled on the other devices. You cannot merge preferences at initial setup for now.
- Upgrade to premium on this Master device (if not already done).
- Now you can enable iCloud sync on this Master device by turning on the toggle at the top of the Preferences page. If a sync has occurred in the past, it may ask you which device to use as "Master". Because it's the Master device, you should click on "Mine" to select local shows.
- On the other devices you want to sync, click on Restore Purchase button in the Preferences page to upgrade Premium on this device as well (in order to Restore Purchase to work, you need to be sure that the same iTunes account is configured on all devices).
- Now you can enable iCloud on these other devices as well. A popup will ask you which shows would you like to use for iCloud. Because it's not the Master device, you should click on "iCloud's" in order to apply the preferences of the Master device to this device.
- Repeat step 4 and 5 on as many devices as you wish to use iCloud sync.
- Now you can freely add or remove shows and mark as watched an episode on any of your devices and it will sync to all the other devices almost instantly.