I'm looking to use pro sites to charge users monthly

Hello

I'm looking to use pro sites to charge users monthly to create their own Wordpress site on the network.

I would like to have one of the websites on the network (the main website) to display the features available and the payment form to create a website etc. Similar to some the example websites.

How would I go about applying the 'register a site' form to the main website on my network?

Many thanks

Elliot