Go to your device's Settings, scroll down to Mail > Accounts>Add Account.
Enter your full email address, password, and a description of your account. Tap Next.
NOTE: If you aren't sure what your Exchange email address or password is. Contact your organization's administrator.
If you need to enter additional server settings, ask your admin or contact your email provider for details.
NOTE: You can also see POP and IMAP settings for Office 365 for Business and go to the section titled "POP and IMAP settings for Exchange-based email" for helpful tips. POP and IMAP will only sync email, not calendar or contacts.
The Mail app may request certain permissions such as accessing your calendar and contacts. To agree, tap Yes.
Now choose what you want your email account to sync with your iOS device and tap Save.
Now you're all set to go!