Answer:
If you have a tower pressure cooker with weights on top...say you were making pea soup then half fill pan with peas and water, place the lid, place the weights on top, turn gas hob on full to you hear pppsssss, then just lower the temp and leave for 10 min. Gently release the pressure by lifting slightly the weights. Really the same procedure for the prestige pressure cooker too. Don't be afraid of it as it is invaluable cooking aid...have fun.