After you have enrolled in Multifactor Authentication (MFA), your account is protected by your password and a time-based one-time password (TOTP). You will need access to the device you enrolled with in order to log in to your Office 365 account.
You will still be prompted for your ATU username and password on the normal Arkansas Tech Single Sign-On Screen. Enter your ATU username and password here.
You will then be redirected to a page on Office 365 to authenticate your login with the mobile app or the passcode you received in a text message. You can bypass this step on trusted devices for 30 days by checking the "Don't ask again for 30 days" checkbox.
After you authenticate your login, you will be granted access to your Office 365 account.