The Diary iOS app was designed to integrate seamlessly with your Apple Health data. You can allow The Diary app to access various health-related data from Apple Health. You can change your settings in Apple Health at any time. If you did not set up your Apple Health integration when you set up The Diary app, you can do it now.
Open your Apple Health App
From any screen in your Apple Health App, touch the "Sources" button on the bottom menu.
On your Sources page, you will see The Diary. Just touch this to get to your settings.
You can change any of the health settings individually here or touch the button on the top to turn them all on.
Once you have done this, the information you have allowed the Diary to see will automatically be put into your Diary app and your Web Diary.