When another user shares a folder with you, you receive a Shared Folder Notification in your Mailbox.
Double-click the notification to open it.
Read any message from the user (if there is one) in the shared folder notification.
Notice the rights you have been given to the folder in the shared folder notification.
Click Next.
(Optional) Change the folder name.
Click a position in your Folder List where you want the folder to be.
Click Finish.
For more information, see About Folders.