How can I play on multiple devices at once?

You can play on multiple devices at once in case you sync your games using your Facebook account, which is the main way to sync your progress. 

There is also a possibility to sync the games via Apple ID / Google Play data. If you had this type of synchronization before, then you can restore your progress using your Apple / Google account data (in the main menu). Make sure you are using the same account as before - otherwise, there will be no way to sync and restore your progress.

Using the synchronization, you can play the game on several devices at the same time and have the same progress and items on all your devices.