How do you secure a wiki?

It appears anyone in the world can make changes to the default install of phpwiki. Now if I go the phpwiki site and I click on ‘edit’ of a page it prompts me for a username and password. How can I make mine do that?

Update: I think I got it. I’m not sure if it’s completley correct, but it appears anonymous individuals can no longer edit current pages or create new ones.