[SOLVED] How to use [recaptcha_form]

I am using Atahualpa 3.4.6 I have configured the WP-reCAPTCHA plugin. It says,

"Simply use the shortcode [recaptcha_form] in any of your posts or pages. All emails submitted from the reCAPTCHA forms will be sent to the email address specified above."

Where do I put this [recaptcha_form] so the comments include a CAPTCHA verification?