to be forwarded to the right Site View, the user that tries to login in the application must be stored in the database and connected to a Group on the Default Group relationship. This group must be connected to a Default Module stored in the database using the id of the Site View and its name.
If you are passing correctly the username and the password to the Login Unit, this will evaluate the relationships between users, groups and modules, and will forward the user to his Default module.
I suggest you also to visit this URL:
How to use the protected modules
that will explain you how to set the protected elements in the Web Model and configure them correctly, while here The Login the login is explained.