To add an event you click the Calendar link on the top tab menu. Choose the date of the event you want to add (if it spans several dates pick the start date) and click the date number in the Calendar box.
This opens the usual message posting screen with four extra options above the usual Subject line box. Make sure you complete them all to make the link and that the Post In: box says Resources - What's On. For multiple days events you choose how many days the event will continue for, and it's added to the Calendar for each of those days, not just the first day.
This info connects the calendar item with the post in the Events forum - so you click the event on the calendar and it takes you to the events forum to see the details.
If you just post an event into the events forum it won't show up on the calendar at all as it's a one-way linking system.
