Use HTML tags:
<b> <i> <u> <small> <blockquote>
One line of code: <code>..</code>
Block of Code:
[code=X]
 ..
[/code]

Refer to a member [user=..]
Spoilers: [spoiler]....[/spoiler]

More: Play around forum • Posting Tutorial

Attach files to your post use the Attachments button and Browse or drag and drop. Images are automatically resized. Inline images from external sites are usually automatically copied over as an attachment. Insert an attached image anywhere in your post using the syntax [att=N] where N is 1,2,3,4 for the 1st, 2nd, 3rd, 4th attached image. Animated GIFs are preserved if they are not too huge otherwise the preview is just the first frame.

No special rules have been set however the general site rules apply.