Remove primary domain from addon domain

Hi,

I am hosting a wordpress site on bluehost. I want to run a completely separate wordpress site without any connection to my primary domain.

I added my second domain to bluehost as an addon domain. This created a new directory in public_html and set it up as subdomain.primarydomain.com. I installed wp in this directory and logged in.

I want the domain to appear simply as subdomain.com. I tried changing the site url to http://www.subdomain.com but it loads as a blank page.

Any help would be greatly appreciated. Thanks