Thank you so much for your help.
I used this link http://www.totalchoicehosting.com/help/wordpress.html to install, I am assuming that was a manual install? So by install a copy of wordpress in the sub folder, are you meaning go through the steps in the link above again with the sub domain folder?
Also, once I have this done, when the subdomain address is used will the blog open in a page? I mean is there a default blog page address like my index.html in my public_html folder?