Noob Question: Does anyone know how to change how posts look?

Update: Still an issue but now that I'm looking around xenforo, that's how it should look!

Hey everyone, haven't been around in while, hadn't been feeling that great and only now been getting better. Diet change, more exercise etc. Anyways, I want to make my forum look better, not sure what happened but my style has changed the formatting of each post, and now I'm stuck with large spaces (i'll show in picture), and then the post. I ended up trying to fix it by adding a background which...