The app allows you to copy its data between iOS devices via email or via iTunes. The easiest way is via email. First you need to create a backup of your data. You do that from the Backups screen, which is accessible via Settings tab on iPhone or under Actions menu (third toolbar button from left) on iPad. Once on Backups screen, you will see several backups already made - these are automatic backups that the app is taking every week or so. When transferring data between devices it is a good practice to create a manual backup to make sure that all recent changes are included. To do that - tap the Edit button and then the + button that will appear. You will see a new backup now listed at the top. To email this backup, tap it (make sure NOT to tap its icon, that is reserved for transferring data between free and paid versions of the app on the same device) and choose Email as Attachment to send yourself a copy of the data. To restore the data on another device - open the email there and tap the attachment in the email, then follow the steps.
It is also a good idea to create manual backups periodically as you change your data and send yourself a copy in case you need to restore it later.