Start off with paragraphs and headings. Using the h3 tag will give you something like below. 

[h3]Heading[/h3]
Then add your text underneath, like this lot here. If you want more info on other ideas, check out [url=https://www.roleplayerguild.com/topics/153116-the-art-beauty-of-bbcoding-complete]this article[/url] for more information on BB coding.

That should get you started, but don't go too overboard on design until you master the idea of laying out for information convenience. 

Note: the little tabs you are referring to may be hiders

[hider=like so]
Example
[/hider]

(sorry if it's a shotty sounding post. Pretty late for me at the moment)