Tap Settings > Mail, Contacts, Calendars > Add Account > Microsoft Exchange.
Your iOS device will now try to locate your Exchange Server. If necessary, you will need to enter your front-end Exchange Server's complete address in the Server field.
Choose which content you would like to synchronize: Mail, Contacts, and Calendars. Tap Save when finished.
Note: To modify your exchange settings, Tap Settings > Mail, Contacts, Calendars, select your Exchange account, and tap Account Info.