It's easy to connect to and synch with Apple Health and/or an Apple Watch on iOS.
To start, navigate to Settings in your main (left) navigation menu.
On the Settings tab, scroll down to the Carb Manager App Settings section, then the Fitness Device Links subsection. Toggle Connect with Apple Health / Apple Watch to On.
Carb Manager should then begin syncing with Apple Health and/or your Apple Watch.
Important: These settings do not appear on the web version of the app. You must follow this step directly from your mobile device.