Users have the ability to link all accounts to the same identity login. Once all instances have been created and linked to the same identity, they will be able to switch between accounts by going to the Switch Account menu option on the login page. Here, select the user role type for this session.
Now, select the agency and that will log you into the system with the access type that was selected in the previous step.
If you are already logged into the system, you can switch roles by using the Switch Account option in the drop down menu on the right of your screen.