To create a new page, just make a name for it and surround it with double square brackets like so: A New Page. When you save the page, the link will show up and you can click on it to create the new page.
For PCs and NPCs in your campaign, use the Character Link button to the right.
HTML and Textile
To style things how you want, we use a simple formatting language called Textile. Textile is easy to learn and simultaneously allows for lots of customization.