If you need to set up a new WordPress site on THE SAME SITE as your existing site, then you should be able to take advantage of the cloning feature. Create the new Worpress site in the usual way but in a subdomain, possibly using Installatron or similar built into the hosting area, and when you have finished developing your new site use the Clone utility to move it to the root level, thus replacing your current non-wordpress site. Now you can delete the original site.