https://www.prestashop.com/forums/topic/442633-add-recaptcha-to-prestashop-version-16014-for-free/
Step 1) Setup your Google reCAPTCHA Account @ https://www.google.com/recaptcha/intro/index.html
Step 2) Download «EICAPTCHA-MASTER.ZIP» below. To install you will need to do this manually by uploading the ZIP file to your MODULES folder, Extracting it and Renaming it to EICAPTCHA. Bit of a pain I know. Lo tengo descargado en el repositorio de modulos.
Step 3) Configure your EICAPTCHA Module and enter your PUBLIC KEY and SECRET KEY, SAVE
Step 4) Open «contact-form.tpl»
<DIV style="text-align:right;" class="submit"> <BUTTON type="submit" name="submitMessage" id="submitMessage" class="button btn btn-default button-medium"><SPAN>{l s='Send'}<I class="icon-chevron-right right"></I></SPAN></BUTTON> </DIV>
For me it was on Line 141
Directly above this div place the following code:
{if $captcha} <p> <script src='https://www.google.com/recaptcha/api.js'></script> <div class="g-recaptcha" data-sitekey="YOUR_PUBLIC_KEY"></div> </p> {/if}
NOTE: Be sure to replace «YOUR_PUBLIC_KEY» with your Google Public Key
Step 5: Save «contact-form.tpl» and upload it to your «theme/yourtheme/» folder via your FTP Program
Final Step: Refresh your browser and test your RECAPTCHA