Creating a new page
To create a new page, make a name and surround it with double square brackets like so: A New Page. When you save the page, the link shows up and you can click it to create the new page.
Linking to existing pages
To link to existing pages, use the same double square brackets. For example, here’s a link to the this page: Main Page
Linking to a page with different text
If you don’t want to use the page’s name as the link text, you can specify your own text by placing a vertical bar | and the link text like so: The Text To Display
Linking to characters
For PCs and NPCs in your campaign, the easiest thing is to use the PC/NPC Link Lookup in the sidebar. Otherwise, the links behave much like a wiki link, just with a colon at the start.
HTML and Textile
To style things how you want, you can use either HTML (with some restrictions) or a simple formatting language called Textile. It’s up to you, but Textile is pretty easy, while simultaneously allowing for lots of customization.