How to use Recaptcha with Login !!!

Hi,
I have tried reading a lot of stuff ( code ) on google and still ended up with a 500 internal server error while displaying the home page.
All i am trying to do is to configure Recaptcha on the Register page or the login page ( my home page on a test site ).
Can anyone please help me if possible or is there a step by step guide on the forum ( modx forum )...

I have gone through this link:- https://developers.google.com/recaptcha/docs/display
Thanks..

hi,
since i have modx version 2.4 so i have raised the question in that section of the forum again...