You can use code like this http://prntscr.com/j0a9ag:
<p>Your Name*<br />
[text* your-name] </p>
<p>Your Email*<br />
[email* your-email] </p>
<p>Website<br />
[text your-website] </p>
<p>Your Message* <br />
[textarea* your-message ]
</p>
<p>[submit "Send Message"]</p>
Please read there articles – https://contactform7.com/captcha/ https://contactform7.com/2015/09/17/contact-form-7-43/
Regards