How to Add Shared Exchange Mailbox to Outlook

Step 1 - In the Outlook desktop app, click 'File'

Step 2 - Choose Account Settings, then select Account Settings from the menu.

Step 3 - Select the Email tab.  Make sure your Exchange email account is selected, then choose 'Change...'

Step 4 - Select 'More Settings'

Step 5 - Click the 'Advanced' tab, then click 'Add'.

Step 6 - Type the name of the shared mailbox you want to add, then click OK.

Step 7 - Choose Next > Finish > Close.