To Share a Microsoft Office 2010 Outlook Calendar
Open Outlook
Click Calendar
Select the Calendar you want to share
Deselect the calendars you don’t want to share
Click Share Calendar 
Add the people or group’s that you want to share the calendar with
If you want them to be able to edit the calendar check the box “Recipient can add, edit, and delete items in this calendar’
Click Send
You will get
or 
Click Yes
The person you shared the calendar will now receive an email like this
They will now have to click the “Open this Calendar” button at the top.
They will now have access to the shared calendar.
