The following image shows the Events Management page.
Here you can add events to your calendar. To add an event, navigate to the correct month and click the date. A form will appear to allow you to add information about the event.
Firstly, choose whether to make the event a yearly event or a one-off. Next, give the event a title and description. Html is not allowed in either of these. Lastly, you can link this event to some categories. Use ctrl-click to select multiple categories. Click "Add Event" to confirm the event.