To switch between reading rooms and to switch between prod and test Aeon instances, you need to use a tool called the SQL Alias manager (SAM). The best way to find it is to search in your Start menu for SQL Alias Manager or SAM. This tool is used to change between "connection files" (a.k.a. "DBC files" or ".dbc files") which contain the information needed to select how you want to connect to Aeon.
Once you have opened the SAM, you should see the screen below. If you already have the option for "Aeon Test" as shown in the screenshot, skip to Setting the Desired Instance below. Otherwise, to start, click on the open button.
and then paste into the filename box:
And press enter. This will bring up a directory with connection files for all Atlas products. You will need to paste the whole address since many people's network accounts will lack the permissions needed to browse the rest of the Atlas operational files.
Each directory contains a default file for the pertinent instance. This file is named Aeon.dbc for production and AeonTest.dbc for test. The other files within each directory are reserved for special use and labeled with reading room suffixes. Choose AeonTest.dbc and click Open.
You can then press "Set Default (Current User)" and the connection will change.
Once you've added a connection file it will remain available until the file is removed from the \\storage.yale.edu shared directory or until you can no longer access the directory, so switching between Prod and Test should be easy. Unless advised to do so by Aeon support staff, don't copy a .dbc file from the shared directory straight into the application folder. It will override anything you have set in the alias manager but not get updated if the network fileshare version does. Only the .dbc files from the \\storage.yale.edu addresses should be used since they're kept up to date. If there's ever a change for security or other reasons then that's the file that will be updated.