1. Install Agilent IO library 16.0 (the software is in CD)
2. Open IO library, choose tools->option->Agilent 488 option, and check enable agilent GPIB cards for 488 programms. The7470 plotter emulator is designed for NI GPIB card, and this option in IO library provide a NI GPIB simulation mode
3. install HP7470 plotter emulator and run Prologix GPIB Configurator, it will automatically find a NI GPIB interface
4. I think you are using 8590A, so check your 8590A GPIB address and HP7470 plotter emulator, select Acquire and choose "request plot from supported device at XX address"