M1 Spend integrates with a number of cash transfer apps including Venmo, Cashapp, and Zelle. In order to connect with third party cash transfer apps, you will need to input your 16 digit debit card number within the transfer app. At this time, M1 Spend does not support Plaid connections so you will not be able to connect your M1 Spend account to a third party app using your M1 login credentials.