How do I authenticate or log in to the ESPN app if I subscribe with a …

Launch the ESPN app and log in using your ESPN.com credentials. The first time you try to stream any content you will be prompted to log in with the username and password your TV provider issued. As long as you subscribe to a TV package that includes ESPN and the account is in good standing, you will be able to view all streaming content that …  

https://support.espn.com/hc/en-us/articles/115003814292-How-do-I-authenticate-or-log-in-to-the-ESPN-app-if-I-subscribe-with-a-participating-provider