JOOMLA FORM USING RS FORM PRO

We have a website running Joomla and has RS Form Pro installed and working well. We need to create a form that has a hidden field; if the user selects yes, then we need to show the fields. The demo is on the vendor's website <[login to view URL]> We need a coder to adapt this example into our form so that if the user selects YES, then we show other fields or a drop down menu. That's all.