Step 1: Open Outlook, and find the Folder List
Step 2: Right click on the folder you wish to share.
Step 3: From the menu that appears, select Properties, and then click the Permissions tab.
Note : If there is no permission mode assigned for the folder that you have chosen, you would need to set up the permission. In order to grant permissions, set the default delivery location to your Microsoft Exchange mailbox.
Step 4: Click Add and select the names you want to share with from the Global Address List. After each selection, click Add->. When you are done, click OK.
Step 5: You can now select which permissions to grant. If you wish to grant only the ability to view items in this folder, assign the role of reviewer. Also, you can set other permissions based up-on your need.
Step 6: Once you are done, click on ‘Ok’ button to save the changes.