Hi there,

For a WordPress website, I would recommend using a plugin to do that.

For example, I could suggest this plugin here:

https://wordpress.org/plugins/google-captcha/

You can install the plugin by following these steps here:

• Upload the google-captcha folder to the /wp-content/plugins/ directory.
• Activate the plugin via the Plugins menu in WordPress.
• Plugin settings are located in reCaptcha menu.
• Create a form in post and insert the shortcode [bwsgooglecaptcha] into the form.

Hope that this helps!
Regards,
Bobby