Pressure Cooker - help please

I was recently given a pressure cooker with garbled verbal directions and I am not happy to use it unless I know how it works properly.
Do you cook food until simmering and then clamp lid with valve on and if so how do you know when the food is cooked? The valve lifts off easily and the cooker is an older one, french made and the brand could be SEB.
Thanks to any who can help.

I've used mine for years,but I know some people are nervous of them.With stews and such,you only need an inch of water,if vegies are included.Put everything in,(veg under meat)clamp lid,put on high heat.When it is sounding really pressured-up,like something awful might happen(!),simply turn the ring down to medium-low.For a stew I would leave for 30-45 mins.Pick the whole thing up and place in the sink.Run cold water over the top/sides,for a minute or so to de-pressurise.It may suddenly hiss-that's okay.To check if de-pressurised,lift the weight.There should not be a gust of steam.Once assured,take out of sink,undo lid.With a stew,I then make a cornflour and little water mix,and trickle in,stirring with wooden spoon.Let cook a couple of minutes over low heat.Amount depends on stew quantity.Remember-season well,lots of flavours,and always some brown sugar!!Enjoy!

I have an older SEB and just looked at the book from it.This is the instructions:

1. To Reckon Cooking Time
Place your pressure cooker on the heat.As soon as the rotating valve begins to turn, the necessary cooking pressure has been reached.It is only from this moment on that you must count the cooking time indicated for each recipe.
2. To Reduce Heat
Reduce heat so that the rotating valve remains still while releasing a little stream from time to time.If you have a recipe to be reduced or boiled down, lightly increase the heat so that the valve turns slowly.
3. To Lower the Pressure
When the cooking time is over allow steam to escape and lower the pressure.Simply lift the rotating valve up to the first notch.You do not need to remoive it entirely.To speed up the process when the pressure is not full you can slowly loosen the tightening knob by turning in the opposite direction to the arrow until steam starts to escape downwards around the lid.When all the steam has been released remove the lid.
4. To remove the lid.
Turn the knob in the opposite direction to the arrow.The clamp must be touching the lid.Lift the lid to disengage and slide it out horizontally.If you have not opened your pressure cooker as soon as the cooking has ended the steam inside will hold down your lid.In this case reheat your pressure cooker for a few seconds with the tightening knob open and the lid will then loosen on its own.

I hope this helps, my SEB has a sort of curved bar across the top of the lid and the knob on top of this.

thanks for your help, much appreciated.