This solutions article provides the steps to add a shared mailbox to the Outlook App on a Samsung phone. Please note that your account must have full access to the shared mailbox for these steps to work and you will need your O365 password.
Outlook Mail App
1. Open the Outlook App
2. Click the Microsoft Icon at the top left of the screen next to the word Inbox
3. Click on the envelope with a + sign next to it.
4. Enter the email address of the shared mailbox (e.g., shared@flagstaffaz.gov). Click Continue.
· Password: Enter your password (not the shared mailbox password).