1. Click on your image/name in the top left-hand corner of the screen
2. Select "Open another mailbox..."
3. Enter in the shared mailbox's email address

Outlook Desktop App (Windows)
No setup is required. Shared mailboxes will appear under your account folders on the left-hand side.
If it doesn't automatically appear after some time you can force it by doing the following:
Open Outlook.
Choose the File tab in the ribbon.
Choose Account Settings, then select Account Settings from the menu.
Select the Email tab.
Make sure the correct account is highlighted, then choose Change.
Choose More Settings > Advanced > Add.
Type the shared email address
Choose OK > OK.
Choose Next > Finish > Close.
Outlook Desktop App (MacOS)
To open the shared mailbox:
1. On the
Tools menu, click
Accounts >
Advanced >
Delegates
2. Add the mailbox under Open these additional mailboxes
Mail (iOS)
1. Open Settings > Mail > Accounts
2. Choose Add Account
3. Choose Other > Add Mail Account
4. Enter the account information (see next image).
6. Press NEXT to continue.
7. Make sure that IMAP is selected at the top of the screen and enter in settings as shown below
8. Choose NEXT and wait for the server to verify your settings. When complete choose SAVE.