Use this method if you want to view and manage the email rules for the shared mailbox in its own browser window.
Sign in to your account in Outlook on the web.
On the Outlook on the web navigation bar, select your name in the upper right corner.
Choose Open another mailbox
Enter the email address of the shared mailbox that you want to access and select Open.
Another Outlook on the web session opens in a separate window, allowing access to the shared mailbox and create the Email Rules within the Mailbox