Adding a shared mailbox with it's own Outlook profile

To add a second, fully independent profile for an account (either a delegated user mailbox or shared mailbox), do the following

1. Open Control Panel
2. Open Mail
3. Click Show Profiles
4. Click Add
5. Give the profile a name, then click OK
6. Choose Cancel, then when prompted if you'd like to create a blank profile, click OK
    
7. Under When starting Microsoft Outlook... choose Prompt for a profile to be used, then click Apply
8. Close Outlook
9. When you reopen Outlook, you will be prompted to choose a profile. Pick the one you've created as a blank:
10. You will then be shown a login window like this: 

From there, you can add any account or shared mailbox as you would any other. Instructions for shared mailboxes can be found here - you will begin at step 3.