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

Device Settings >Accounts & Passwords

Tap

Choose Exchange

Choose Exchange

Enter your Office 365, Exchange, and a description of your account. Tap Next.

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.

The Mail app may request certain permissions. Tap Accept

Tap Allow if prompted to give permission.

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

Account sync settings