1. Tap Settings | Mail, Contacts, Calendars | Add Account (see Figure B)
  2. Figure B

    Add an email account.
  3. Tap Microsoft Exchange. Enter your full email address in the Email field, plus your Username and Password (see Figure C). Leave the Domain box blank.
  4. Figure C

    Enter your email address, username, and password.
  5. Enter the Exchange Server setup information (provided to you while getting access to Office 365 or from your IT staff), and then tap Next. Your iPhone will try to locate your Exchange Online Server. If your iPhone can't locate the server, you'll need to enter your Office 365 Exchange Server's complete address in the Server field on the Account page (see Figure D).
  6. Figure D

    You may need to enter your Office 365 Exchange Server settings on the Account page.
  7. Choose which content you would like to synchronize: your mail, contacts, and calendars. Tap Save when you have made your selections.

While setting up your iPhone for Office 365, you may be prompted to enter a passcode. Enter in a new passcode of your own creation. Whether or not you have to setup a passcode varies on the security setup as established by your Office 365 administrator.