Open the Outlook App, open the Menu (circle with your Initials or Image) next to INBOX > tap Settings  It will list your accounts. Tap to select your umassmed account.(Exchange) This will load the account settings screen.
On the bottom tap Delete Account

Once the account is deleted it will take you back to the Add Account screen, enter your full email address, then tap Add Account.

If you're asked to select your email provider, please choose Office365

Enter your email account password and tap Sign In

Accept any prompts for permission you may receive.

Swipe through the features and you're now ready to use Outlook for iOS!