We do not have a built-in table editor yet (it is in the works right now) so either use one of page templates if you can find one which matches your needs, copy-paste from MS Word or another HTML editor - or go into HTML edit mode and copy-paste table HTML code (there are tons of free table code generators - e.g. http://www.google.com/search?q=generate+html+for+table )
Dmitry Buterin, Chief Apricot