How-To Add a Mailbox to Outlook 2010
1. Open Outlook 2010 and Click File, Info, Account Settings
2. Highlight the account and Click Change
3. Click More Settings
4. Click Advanced Tab then Click Add
5. Type in the name of additional / secondary mailbox and Click OK
6. Verify the new mailbox is listed. Click OK to save
7. Click Next
8. Click Finish
9. Click Close
Done! Your new Mailbox should now be listed below your primary account