From what I have read it is a matter of trial and error because pressure cookers vary so much, but this is generally what you do.
Add raw peanuts in shells, but not more than half full. Add water to cover, and add salt-4-5 heaping tablespoons. Remember-its the salt that "makes" boiled peanuts. Bring up to full pressure, lower heat a bit and cook 10 minutes. Use the cold water quick release method to cool the cooker and lay out the peanuts on a cloth. Test and see if they are done to your liking. Keep experimenting until you have the right combination of time and salt to suit your taste. I LOVE boiled peanuts which is why I never make them. They are totally addictive!