You can start the Legacy Desktop for multiple instances of the Platform via the Desktop Launcher application, or you can start it in your browser.
When the Desktop Launcher connects to the Platform, it will automatically download and install the various files that are required to run the Desktop. After a system upgrade, the Desktop Launcher or Desktop in your browser will update these files to ensure that the Legacy Desktop is compatible with the connected Platform.
If a new version of includes an updated version of the Desktop Launcher it will update itself.