Before you configure the extension for use, you need to register your domains with Google reCAPTCHA. Go to http://www.google.com/recaptcha/intro/index.html and click “Get reCAPTCHA”. Here you will find a form to register for reCAPTCHA for use in your domains.
Google reCAPTCHA: Option to enable or disable reCAPTCHA if needed.
Site Key: Enter the site key you have got while registration for Google reCAPTCHA.
Recaptcha Theme: Select the Recaptcha theme from the available options.