By default, everyone has the ability to view the availability of other's within the organization.  In some cases, you may be given editing rights to anther's calendar. In either case, you can use the following to quickly add someone else's calendar to your Outlook's list of calendars.

Note: you may only one instance of a calendar added at a time. If you add a calendar, but it does not show in your group, you may have that calendar added to another group already.

1. Open the Calendars tab in Outlook.
   
2. Right click the Calendar Group you want to add the calendar to, then choose Add Calendar > From Address Book.
   
3. Double Click any calendar you would like to add.
   1. Double clicking will add the calendar into the Calendar box at the bottom of the window
      
4. Click OK and wait for the calendars to populate