When using iStation from a Chromebook, you will not need to sign in at the login screen.
Simply click the Apps button at the bottom of the login screen and select iStation:
The first time you use the iStation app, you will need to enter your campus domain information. You can start to type in the name of your school to bring up a list. We recommend having the classroom instructor do this, as a complete uninstall is required to remove the settings.