Create a free Group account right from the app if you have not already done so. This will upload your information to the web portal & backup current data (not history).
Sign-in to the same Group using the other device app.
Choose "Use group data" when prompted in the device with "less data". This will download your information to it.
Choose "Merge the app and group" on the device with up to date date.
Use a computer web browser to sign-in at the Web Portal www.grocerygadgets.com to work with your data and the information will be synced to your iPhone and vice-versa.
In case you want to have a history of back ups, use your iTunes backup tool.
You can also sync your devices by sending an email invitation with "Invite Others" tool.
If you forgot your password and can't sign in to your Group - press "Forgot password" and recover your password by Group Name or by Email.
You can also recover your password through the Web Portal www.grocerygadgets.com