The dried shrimps keep for a couple of weeks if refrigerated, so don't feel you have to rush home and cook them immediately.
I soak them in cold water for about 5 hours, changing the water at least 5 or 6 times. You could soak them overnight in the refrigerator ... up to you.
it was at this point I realised I had too many shrimps for the amount of tomato's I had added. I checked my cupboard and saw that I had a large jar of pasta sauce, so added that as well.
Keep stirring gently and adding water when needed, over the cooking time of approximately 2 to 3 hours, I had added about 5 cups of water.