To get the google reCaptcha Keys at first login into your mail address & follow the procedures-
1. To register new site go to www.google.com/recaptcha , click on MyreCAPTCHA.
2. Enter “Label” name as your site name & “Domain” name that is your site url.
NB: Please remove “http://” when you put your url.
3. Choose type of reCaptcha.
4. After registration get the secret & site keys.
5. Put those keys into admin panel API credentials.