Configuration file path is specified with Apache directive (/etc/httpd/conf/gsweb.conf is an exemple):
GSWeb_ConfigFilePath /etc/httpd/conf/gsweb.conf

The format is GNUstep/OpenStep property list.
Here is an exemple with all the possible options:
{
  //Global Parameters
  canDumpStatus = YES;  //YES if server can display status (URL: /GSWeb/status)
  GSWExtensionsFrameworkWebServerResources =
    "/GSW/GSWExtensions/WebServerResources";  // URL of GSWExtensions
                                              // Framework
                                              // WebServerResources directory

  //List of applications
  applications = {
    //The 1st application: MyApp
    MyApp = {
      //List of its instances
      instances = {
        //First Instance
        1 = {
          host = 145.146.147.20;  //Host of this instance
          port = 9001;            //Port of this instance
          parameters = {          //Unused
            transport=socket;
          };
        };
      };
    };

    //The 2nd application: AnotherOne
    AnotherOne = {

      // URL of GSWExtensions Framework WebServerResources directory.
      // It overides Global parameter
      GSWExtensionsFrameworkWebServerResources =
        "/GSW/GSWExtensions/WebServerResources";

      // YES to say that this application can be listed when the
      // adaptor don't find an application
      canDump = YES;

      //Unused for the moment
      applicationHeaders = {
        header1 = 1264;
        header2 = 4567;
      };

      //Instances
      instances = {
        //1st instance
        1 = {
          host = 145.146.147.20;
          port = 9002;
          parameters = { 
            transport = socket;
          };
        };
      };
    };
    MyAppVoid = {
      // Here we have 3 instances
      instances = {
        1 = {
          host = 145.146.147.20;
          port = 9001;
          parameters = { 
            transport = socket;
          };
        };
        2 = {
          host = 145.146.147.21;
          port = 9002;
          parameters = { 
            transport=socket;
          };
        };
        5 = {
          host = 145.146.147.22;
          port = 9003;
          parameters = { 
            transport=socket;
          };
        };
      };
    };
  };
};