See how I disassemble and reassemble the side plate on a P08 Luger (also known as Pistol Parabellum). You'll need to take out the trigger lever pin out with a brass screwdriver.
Be sure to follow all disassembly and assembly instruction found in the technical section of http://www.lugerforum.com.
If you are not sure of what you are doing or if the gun is not working properly, take it to a competent gunsmith.
Be sure to follow all NRA firearms safety recommendations.