Add your Exchange account
Tap Settings > Mail > Add Account > Exchange.
Enter your information
Enter your email address and password. You can also enter an account description ie 'Work email' (optional).
Connect to the Exchange Server
Your iOS device will try to find your Exchange Server. If the email address and password have been entered correctly and are still valid you will notice ticks appear briefly to the right hand side of the details you entered.
Sync your content
You can sync Mail, Contacts, Calendars, Reminders, and Notes. Slide the switches on for the types of information you would like to sync, normally you would enable everything. When you're finished, tap Save.
If you are prompted with a question 'What would you like to do with items already on the iPhone?' Tap 'Keep on my iPhone'