Please read the detail on the HealthPlugin component that has the necessary starting points to the documentation.

Besides that, to try this Demo application by your own, you will need to:
1. Configure a keystore and project on Google API Console (for Android devices & Google Fit). Get more details here.
2. Edit this application to configure the correct Bundle Id (which identifies the app that you are using to get/set data from/to Google Fit app - check image below).
3. You will need to have Google Fit installed and configured on your device. This is mandatory since the information that you are setting/retrieving comes from the data stored on the Google Fit app installed on your device.

(referenced image on point 2)