Test Site

I’m currently running a site using software which enables me to update my site on my computer and then upload it to the web. I’d like to move to WordPress because I want to be able to edit the site via the web.
I’d like to run it as test first though, whilst maintaining my existing site exactly as it is. So where should I load it to? I use cPanel. So should I make a directory within my public_html directory or can I use the one labelled www (I’m not really sure what that is for?) or another place altogether?