It just doesn't show up at all. Placed right before the form ends. I also use a combination of PHP and Javascript to create my own captcha. PHP generates a random string which I send to Javascript to hold. Upon clicking a button, if what is in the captcha does not match what is in the Javascript, thou shalt not pass. Haven't had any bot break through it yet, but I did have a Russian hacker email me, pissed off (entire email was in Russian, but I'm pretty sure the translator did well to know he wasn't happy), because he had created a bot specifically for my website that managed to create over 2000 posts in less than an hour.

You can view the captcha at https://mypost.io/ .. you cannot create a post without entering the captcha. I ended up creating my own because despite entering the correct answer (selecting the right images), Google Recaptcha would not recognize it.