Go to your iPhone or iPad's Settings > scroll down and tap Accounts & Passwords > Add Account.

Note: If you're on iOS 10, go to Mail > Accounts >Add Account.

Device Settings > Accounts & Passwords

Tap "Add Account"

Step 2 
greyline
Select Exchange.


Choose Exchange


Enter your Office 365, Exchange, or Outlook.com email address and a description of your account. Tap Next.

Where Troussell@contoso.com - Please enter your email address.  Description Can be anything. It does not have to be Exchange. 


Exchange Sign In

Tap Sign In.

Tap Sign In if using O365 or tap Configure Manually if you have your organization's server settings.


Enter the password associated with your email account. Tap Sign in or Next.


Enter your O365 work or school account password.

Step 5 
greyline
The Mail app may request certain permissions. Tap Accept.


Tap Allow if prompted to give permission.

Step 6 
greyline
Choose the services you want to sync with your iOS device and tap Save. You're done!

Account sync settings