Double square brackets round the text. [[Wiki page name]] alternatively [[Wiki page name | what you want to appear]] both of those will create a page called "Wiki page name" but one will show "what you want to appear" in the text.
It's all there on the right of the screen when editing a wiki page.
Comments
However, an "add a page" button would be more useful/intuitive than the current system.
As a stopgap, maybe automatically including the method to create a new page could be dropped into the "GM Only" section of the main page?
It's all there on the right of the screen when editing a wiki page.
...Troels