In order to use two way reports, users must be either Designers or Data Editors, a new user type we've added as part of this functionality. You can designate users as Data Editors through the User page by checking the 'Should this user be able to edit data?' flag.
For some connections, you can also do a bulk import of users by clicking on the 'Import Users' link on the data source page:
This page will pull the list of users from your data source, allowing you to flag what user type each user should be imported as. You can customize the email going out to the users, or mass generate links that you can then send to the users.
