How to add a shared mailbox on Office 365

Step 1: Sign in with your Office 365 admin account at “https://portal.office.com/adminportal/home.”
Then in the Admin center, go to Groups > Shared Mailboxes.



Step 2: On the Add a mailbox page, enter a name for the shared mailbox. Then the wizard chooses the email address, but you can edit it.
After that Click Add. It may take a few minutes before you can add members.

Step 3: Under Next steps, choose Add members to this mailbox.
Members are the people who will be able to view the incoming mail to this shared mailbox, and the outgoing replies.


Step 4: Choose the +Add members button. Put a check mark next to the people who you want to use this shared mailbox, and click Save.
When finish, Choose Close.



Credit : https://www.unifeyed.com/portal/knowledgebase/27/How-do-I-add-a-shared-mailbox-on-Office-365.html