Open Solitaire on your second device. On the Main Menu, tap Settings. Then tap Subscribe to Premium. Finally, tap Restore subscription.
You must use the same Apple ID or Google Play Account you used when purchasing Solitaire Premium on your first device. This means you will have to use the same type of device (Apple or Android, the subscription will not transfer from an Android device to an Apple device or vice versa) The expiration date and term of your subscription will not change.

Note that the statistics are not transferred, only the premium benefits.