You can configure the UserRoles in the Modeler. You can find that in the project explorer (treeview) under project / Security, when you change the security level to demo or production it allows you to create and configure userroles.
Usernames and passwords should never be stored in the Modeler. That would be a security risk.
It would probably be easiest if you take a look at the video's in the online introduction course "Section 9 - Security" shows you how to setup the Security for your application
9.1 explains how to set it up in the Modeler (9 minutes),
9.2 shows you how to actually configure the users (5 minutes).