Adding an account

1. Go to settings | email + accounts | add an account | Outlook
2. Provide Office 365 login email and password
3. Once setup, the account will default to the name Outlook (or Outlook #)
4. In settings | email + accounts, tab the Outlook entry once and you’ll be able to change the name to something more meaningful, like Office 365

Office hub

1. Now in the Office hub, you can connect to your Office 365 account. 
2. The first time you login it will open a web browser control and ask you to login.  You can choose to remember login and password to skip this step in the future.
3. Once authenticated, you’ll see the a view of the lists and document libraries from your Office 365 team site

For those of us keeping itchy to write our own SharePoint - WindowsPhone applications, Microsoft cheated here and the web browser control used in step 2 is accessed via COM to obtain the cookiejar file, which contains the tokens for the Office hub to talk to Office 365.