Wordpress Multisite Custom Installation

Hi,

I have setup Wordpress Multisite and a number of the plugins.

How do I set it up so that every new site that is registered has the same theme, the same pages (e.g Home, About, Contact Me)

I will be selling an online portfolio site that people can buy and setup with a few simple steps. For this reason I need to have every site installation the same so it acts as a template for them.

Thanks,
Jordan