The configuration editor is included with the ReadStart CodeBench install. It is the default editor for any .config file you click on. If you right click on a configration file in CodeBench you will see a context menu pop up that gives you the ability to set which editor is used to open the config file. The tool remembers your last choice and uses that as the default until you select another editor.
To verify the editor is present, you can double left click on the Debug configuration file that is automatically created when you create the Nucleus System Project in your workspace. This should open thr configuration file in the editor. On ReadyStart 2013.03 and earlier, there was a problem with the editor launching correctly depending on a matrix of the BSP installed and the add-on features of ReadyStart. If you recieve an error when opening a config file, please let me know and I can help you past it.