HOW DO I INSTALL GOOGLE RACAPTCHA IN MY DOLPHIN 7 SITE?

HELP ME PLEASE

THE GOOGLE RECAPTCHA SCRIPT IS SIMPLE TO INSTALL ON REGISTRATION form all it requires is me to edit the form fields and the php page processing the registration 

my problem is that i donot know where to locate this two pages

the registration input tags are not on join.php

i want to see that <form action="" tag

please help me, tell me which folders i can find this pages. note, i dont  need captcha module, i need to use Google recaptcha. thanks

AndrewP sell this integration for $25 http://www.boonex.com/m/captcha-2 however, the standard module in dolphin for the racaptcha is located inside the folder simg