You can create an event by clicking in the calendar where the event should be entered, or using the New button near the top-left corner of the calendar screen.

Clicking anywhere in the calendar will create an hour-long event starting at the time you clicked - you will be prompted for a subject for the event. 

You can add guests for the meeting, a room and a description, and can set the start and end date and time. Click on Save to save the appointment or on More Options to add further options to the appointment e.g. your status during the meeting time and whether the event should be marked as private. 

After clicking on More Options: