To configure the query sent to the supplier, you have to go to Configuration panel on the PDC Simulator home page. Then you have to specify all attributes: sending facility, sending application, the query, the number of rows to return, and the continuation pointer.
You can use this tool as a PDC system using the Send HL7 Message panel. This lets you to generate a query, and then lets you to send a HL7 query to a supplier, using its ip and its opened port.
PDC Simulator has a wsdl which lets you to communicate with this tool. The wsdl is here. The web service of PDC Simulator contains all methods needed to communicate beetween gazelle and this simulator. These methods let gazelle to start communication with the PDC Simulator, to send configuration of the supplier, and to order the PDC Simulator to send a query to the supplier.