This help page covers setting up the google recaptcha module, which is used to help protect your public site from spam comments on public posts.
You will need the "Site Admin" role in order to complete these steps.
Enable the Google reCAPTCHA fetaure
Navigate to: Settings & admin > feature selection
At the very bottom of the list, checkmark the box next to "google recaptcha" and then press save. If there's any delays with enabling the module, refresh the browser.