Pull the slide back and allow the loaded round to fall to the ground. Allow the RO to see into the chamber. When he tells you to, release the slide, aim the pistol at a safe backstop, and press the trigger. He will then tell you to holster the arm. This is a stressful time for RO's so be sure to do it slowly, and on command.
Some people like to catch the loaded round instead of allowing it to hit the ground.
Many RO's do not like this as some accidents involving lost fingers and such have occured. It is best to let the cartridge to fall to the ground. I segregate that cartridge from my match ammo and it gets fired in a practice session.