10 steps to  use  Grape Light:

1. Connect the GR-33 unit and your computer with a midi-cable. Connect the midi-out of the GR-33 with the midi-in of your midi-interface or soundcard. Connect the midi-in of the GR-33 with the midi-out of your soundcard/midi-interface.
2. Start Grape Light.
3. Open the option menue and select the correct midi-ports. 
4. Set the GR-33 unit into "bulk load waiting" mood. Press the system button of the GR and click the right parameter button until you reach this setting. Test the midi-connection with the test item of the option-menue of Grape Light.
5. In  the patch collection menue choose "receive". The Gr-33 unit will send all its data to Grape Light. For safety save this collection as your original (patch collection-menue). You can load any single patch in the "selected patch"-menue in the same way.
6. Choose the patch you want to edit with a left double click.
7. Edit the patch as you like. To be able to hear the effect of your changes, click the "send to GR/Temp" button in the edit-window. The program will send the patch data to the the temporarary memory of the GR. They are not saved and your patch collection has not been modified!
8. To save your changes save your patch collection or patch with Grape Light.
9. Now you can transfer your modified programs to your synth-unit.(patch collection-menue, "transmit")
10. It is possible to save the edited patch in temporary memory of the Gr-33 by pressing the "write" button of your guitar-synth.

I hope this will help a little.
Have fun
Ludger