Before sharing your Fitbit data with your practitioner you should add a favourite practitioner. You can see how you add Preferred/Favourtite practitioners by clicking here.

Once you have added a Favourite practitioner you can click the "Share logo" in the "Your Health Snapshot" box (see image below).

A menu will slide in on the right side of your screen. Select the practitioner that you would like to share your Data with by click on the "+" icon (1), Accept the Sharing Terms and Conditions by clicking the "Accept" box (2), 

after selecting your practitioner and accepting the Sharing Terms and Conditions click the "Confirm" Button.

You have now succesfully shared your Fitbit data with your practitioner!

I hope this helped!