Sharing a Calendar folder in Outlook 2011 for OS/X
1.Select your calendar, and then choose “Permissions" 
2.In the permissions window, click “Add User”, and then choose the individual for whom you’d like to assign permissions: 
3.Once the user has been added to the list, assign the desired permissions:
Note:
To activate the greyed "Permissions" Icon, just click the name of your calendar on the left bar under "My Calendars". When "My Calendars" is selected, Permissions may greyed out. When the name of Calendar individually is selected, Permissions should now be made available.