How to create a new install on a subdomain for a mobile site

Hi,
I want to create a new install at the subdomain /mobile but use the same database and all the same pages, users, posts, uploads from the main database. How would I achieve this? I’ve already attempted $table_prefix = 'main_'; in the wpconfig file but this seemed to have created a completely new site. No pages, posts or users were there.

I’m wanting to do this so I can use WPtap Mobile Detector. It asks for a url to redirect to for each mobile site.

Any help would be very appreciated! I’m a little confused on how to go about this.