If you have access to a shared mailbox in Office 365, you can add this mailbox to Outlook on MacOS using your username and password for authentication.
With the Outlook open, chose File from the menu bar and click Open
In the Open window, choose Shared Mailbox.
Outlook will ask for the email address of the account you want to add. Enter the email address of your shared mailbox here and click Continue.
You will then be prompted with the familiar Office 365 Login for Arkansas Tech. Enter your username and password and click Sign In.
Your shared mailbox will appear in the left pane in Outlook under the folders from your primary mailbox.