Go on your PS3, go to Settings, System Settings, then System Info, and make a note of the IP address it gives you. Then go to your router page with your web browser on your PC (usually 192.168.0.1) and set your PS3 as your DMZ server (by typing in the IP that you got from your PS3 into the DMZ settings tab on your router.
Each router has a different method of setting the DMZ so I'm afraid I can't help you with that
Then, go to ProDG, type in the IP address of your PS3, then prey. c:
Sorry, got two methods mixed up there! XD