PostBBCode is a very simple module and there is no admin section right now. No database is used.
If you want to disable some bbcodes or add your own you have to modify a php file.
All bbcodes are stored as regular expressions in bbcode.php in the PostBBCode module directory. Each entry consists of a array with two elements. 1st is the regular expression which has to match the user input. The second value specifies the replacementstring.
Note: See preg_replace in the php docu for further information.