From the Calendar - start at the
Select “Share Calendar” > “Calendar” from the drop down menu.
Calendar Properties Panel
Select “Add” and add the user you wish to give permission
With the user selected, choose the permission level. Hovering over the permission will display what rights are granted.
Edit – the user can manipulate and delete existing appointments
Delegate – in addition can create appointments
Note: Calendar items marked Private are protected. Most people you share your calendar with see only the time of items marked Private, not the subject, location, or other details. The exception to this is if you select the Let delegate view private events check box.