For PCs and NPCs in your campaign, the easiest thing is to use the PC/NPC Link Lookup in the sidebar to the right. It’s quite handy! 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.