Use the following way to add a shared mailbox to your Outlook on a mobile device.
- Open outlook on your mobile phone
- Click the icon in the top left hand corner
- Now click on the Setting wheel in the bottom left hand corner
- Now click on Accounts
- Click on Add account
- Click Add a shared mailbox
- Enter the email address for the shared mailbox
- Click Continue
This will now add the shared mailbox to Outlook on your mobile phone.