Login to the ATD Events app using your td.org registered user credentials. This is the same login information you used to register for the conference.
If you wish, you can create a schedule online in advance of the conference on the Schedule Builder site. Then, you can download that schedule to the app by logging in with your td.org account in both places.
Please note that the schedule you created will not sync from the app to the website (if created in the app). It will sync only from the website to the app.