I need some help with regards to my multisite network... how new sites can be created?

I need some help. I have recently set up my Multisite Network. As far as i know it has been configured correctly and all things are cool. I just cant for the life of me work out how a new site user creates a site on my network. Obviously i have to create the page for them to 'sign up' on, but i can't find the settings or text that i am to put onto this page so that it configures with the mechanics of setting up a site. I have asked this question about ten times now and so far no one can help me. Any info would be great!!