Please note: This only works Apple <-> Apple or Android <-> Android
To manually sync using the backup service you need to log into your account on both devices.
You can then for example start tracking on your phone during the day putting in your breakfast and lunch.
When you return home on your phone you use the backup service to backup your phone data.
Then you open the app on your tablet and use the restore feature and an exact copy of what you entered for the day will be on your tablet.
So each time you want to synchronize the data between two devices you do the following.
On the device (phone or tablet) that has the latest information you go to
secure backup and do a backup, this copies the latest data from the
device to the cloud.
Then on the device you want the latest information on you go to secure
backup and then choose restore which copies that backup from the cloud
to the device.
It's very important that you only use backup on the device that has the latest information, and only use restore on the device that you wish to copy it to.
Please note: Restoring overwrites all data, it does not merge. This means you can not make changes on both devices independently.