You should be able to add events directly to the calendar now - there is a little icon to press.
The event details are stored right at the bottom of the forum - just like a normal post - so you can change it there if needs be!
You should also be able to add an event from a new topic post - under the message box there are a few sections you can open up by pressing the +, and the calendar is one of those.
Let me know if either of these cant be done, as I am an admin I shouldn't see thing differently, but ya never know!