Instruction for reCAPTCHA

Hello ,
I am a little bit confuse about the way to validate reCAPTCHA.

Should I follow only those instructions : https://contactform7.com/recaptcha/
(does it do all the work and I don’t have to worry about other things)

Or do I also need to fallow the google instruction :
1/ integrate it for the client
asking to past that before </head>
<script src=’https://www.google.com/recaptcha/api.js’></script&gt;
and to past that where Captcha should appear :
<div class=”g-recaptcha” data-sitekey=”XXXXXXXXXXXXXXXXXXX”></div>
2/ integrate it for the server
Send a POST to https://www.google.com/recaptcha/api/siteverify

Let me know.
Thanks.
Alex