9 STEPS
1. Open Outlook and press the Calendar icon at the bottom of the Navigation Pane
2. Click Add Calendar
3. Click "From Address Book..."
4. Type in the name of the colleague or mailbox
5. Doubleclick the desired colleague/mailbox
6. Once the colleague has been selected, Click "OK"
7. Click the "X" to close the calendar
8. Click the checkbox under the navigation pane to open the calendar.
9. You're done!