By default, vBulletin installs with a set of BB code tags, such as [b] and [u], which allow rudimentary text formatting and a few other functions, such as quoting other messages, and embedding code in a non-proportional font.
Should you find that you want to add additional BB codes, an interface is provided to allow you to do so. In the left-menu panel of the control panel, scroll down until you find the Custom BB codes section, and click the add link.
