If you have permissions set, you may open and control another person’s calendar in Outlook. Please follow these instructions for opening a shared calendar in Outlook 2010 (same method can be applied to other versions of Outlook).
Step 1 – Go to your “Calendar” section of Outlook
Step 2 – At the top ribbon, select “Open Calendar” and then select “Open Shared Calendar…”
Step 3 – In the box, enter the username of the mailbox. If you are unsure of the username, you can select the “Name” button and select the user from the list.
Step 4 – Once completed, the user’s calendar will not appear in the left side under “Shared Calendars”. To view the calendar in the main window pane, simply tick the box next to the name. You may now fully control this calendar as if it was your own, including entering new appointments and editing old ones.