If you did not give Fitwell permissions during sign up, all's not lost.

If you view your Activeness tracker on the main screen, you'll see a red exclamation mark and the warning "Permission required." Click on the red exclamation mark to grant access. 

Alternatively, you can click on the hamburger menu on the left top corner of the screen, select settings, and under Activity Sourcesection, you can turn on Google Fit.