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 Outlook from the menu bar and click Preferences

In the Preferences window, choose Accounts.

In the Accounts window, click the + button and click New Account.

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.