We Recommend using the Outlook app from the Apple App Store as it has more features, but you can configure it on the native iOS app. Both options are below
Set up Office 365 Account on the Outlook App (RECOMMENDED)
Open Outlook for iOS. The icon looks like this:
If you don’t have it yet, download it from the Apple Store.
NOTE: Available for iOS devices using iOS 9.0 or higher.
Open the collapsed menu in the upper left corner.
NOTE: First time using Outlook for iOS? Just tap Get Started.
Tap SettingsOutlook app settings > Add Account > Add Email Account.
Type your full email address, then tap Add Account.
Tap Yes or Allow to give Outlook permission to sync calendar, contacts, etc.
Swipe through the intro and you’re now ready to use Outlook for iOS!