To post in the Calender go to the top of the page. In the command line that starts with "Home" you will find the command "Calendar" click on that command and you will be guided through the process of entering an event on the calender.
If you post your event in the calendar, one of the options there is were to post the text.
If you select this board "Event" as the place to post your text, you get the best of both worlds, the event in the calendar and the text posted here.