To set up Captcha verification go to the Widget tab > Edit widget.
In the Calls tab click on the Captcha verification:
Now you can create the captcha keys, here.
Use the label that will make it easy for you to identify the site in the future:
Go to the reCAPTCHA type and choose Challenge (v2) and "I'm not a robot" Checkbox:
Add the domain where you want to apply Captcha verification:
Submit and copy both keys and pas them in the CallPage panel:
And the last step is to Save changes.