You will need a Google Drive or Apple iCloud account to use LegacyApp's full features. Having a Google Drive or Apple iCloud account will allow you to save an encrypted backup copy of your LegacyApp notes, restore your notes when needed and pass them on to your beneficiary when the time comes.
Please remember that without a Google Drive or Apple iCloud account you will only be able to use LegacyApp as a personal organiser on your smartphone and will not be able to store a backup copy of your notes (or pass them to your beneficiary).
You can open a new Google Drive account for free here.
Alternatively, you can create an Apple account here - but you should have this already if you are using any Apple products (like an iPhone or iPad).