On iOS (iPhone and iPad)
Open the "My Creations" tab, then login on both devices with the same account. It will allow you to share your subscription and your templates on both devices.
If both of your devices are sharing the same Apple ID, you can enjoy PhotoRoom Pro on both with only one subscription. To do so, open the "Pro" menu (at the top right of the home screen), then click on "Already Paid?" at the bottom. This should restore your subscription.
Note: PhotoRoom Pro is not compatible with Family sharing. To share your subscription with your family, use Option 1
To share your subscription on 2 Android devices, make sure both devices are using the same Google Play account.