1. Select File > Add Account
2. Enter the email address and click Connect
3. If prompted, enter the password again and select OK > Finish
NOTE: When the account is first added, Outlook will need to process a lot of data. During this time, it may be unresponsive. Please allow time for Outlook to finish this processing.
If you have a lot of existing data in your account, Outlook will take some time to finish synchronising with the Office 365 servers. During this time, folders may appear empty until the sync is complete.