Tap Settings > Mail, Contacts, Calendars > Add Account > Microsoft Exchange.
Enter the information in the fields below, then hit Next:

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.