Store spot prawns frozen until you're ready to use them, then defrost as many as you need.
How to Defrost Food with Best Quality & Safety
Spot prawns can be prepared and used as you would other shrimp as long as their sweeter flavor is taken into account. Some people feel they are best served with the shell on, butterflied down the back and very lightly broiled with garlic, lemon and butter.
Shrimp & Prawn Recipes