In the left pane of Outlook you can select to display a list of Favorite Folders. It is possible for this list to disappear and/or for the option to display them to disappear.

If the folder list is hidden, you should be able to just click the chevrons next to Favorite Folders and display them.

If the option to display them is missing or the words "Favorite Folders" are missing you need to do the following.
•Close Outlook.
•Click the Windows Start button in the lower, left corner of the screen.
•In the field where your cursor is flashing, type "Outlook.exe /resetnavpane".
•Start Outlook.

You should now see Favorite Folders again and be able to display them