Office 365 - Outlook 2016 - Open Shared Mailbox
The Outlook 2016 desktop client will natively recognize items that have been shared with you, such as mail folders, calendars, address books, and even fully delegated accounts.
If you have permissions to a shared mailbox, the shared mailbox will automatically display in your Folder pane in Outlook 2013 and Outlook 2016.
NOTE: If the administrator of the shared mailbox has only recently provided you access to a shared mailbox, it may take a short time, such as an hour, before the shared mailbox will automatically appear in your Outlook profile. If the shared mailbox does not automatically display in Outlook, you may need to restart Outlook to see the shared mailbox.
See the linked PDF file for documentation with images: Outlook 2013 Access a shared mailbox.pdf. Although the document is from Outlook 2013, the behavior and appearance of Outlook 2016 is similar.
If you have questions, please contact the ITS Help Desk at 608.342.1400 or email@example.com. You may also visit the Help Desk on the first floor of the Karrmann Library.