To do a link:
[URL=http://www.someurl.com]this is a url[/url*]
Like that, but without *.
Or use the 'instant ubb code' bit at the bottom.
to link to another post... the format is
http://forumserver.twoplustwo.com/sh...ber=IDofThread
Or
http://forumserver.twoplustwo.com/sh...ber=IDofThread