When you have each article of clothing set up, your ready to let her rip. Hitting the Calculate Simulation will only calculate the current item, to calculate all at once...

I found that after so many calculations, P5 doesn't want to do it anymore. You can delete the simulation recreate it, and most of your settings are retained and you can continue.

When it's done calculating you can hit play/pause, or frame advance to pick your frame. Move the camera and lights if neccesary and render your still. If you want to change the final pose, go to the end frame, alter it, recalculate and render.