captcha recaptcha

I want to add captcha -recaptcha to my custom form.
I tried with google plugin but not able to do
Help
Tamanna

You created custom form using what?

I created custom form using php.
wrote html in article and created a form in html linked to php.
Put public and private keys in google recaptcha,changed global settings.What else to do?
Thanks
Tamanna

We don't provide support for such cases only for template bugs and help configuring. Search google there are plenty examples of how to code captcha using public captcha providers (external sites that provide you with image and validation mechanism), joomla itself uses such service:

www.captcha.net/