Where to write the Utility scripts to accept the command line arguments

You add it as a script routine in a script unit in TestComplete.  There's no specific "utility" section of TestComplete.  

The script as presented in that article simply demonstrates how to use the BuiltIn.ParamStr and BuiltIn.ParamCount methods of TestComplete to find and parse out values.  So, if you need to obtain a commandline parameter passed to TestComplete, you would adapt that script to find that parameter and value and then pass it along to whatever variable, method, or test that needs that value.