It's very easy, don't worry, you will do it more than fine. To be honest, you are on a serious amount of oxy, let's hope for the pods to be decently strong.
You want the pods and the first 10 cms (3 inches, I think) of the stem. I mean the part of the stem united to the pod, no to the roots.
You crush the pods and get rid of the seeds. You can grind it very finely or just crush it with your hand in some pieces. Some people swear the smallest the best, some of them even grind them in an electric machine for coffe grains, sorry about my English, I don't know how do you call it. I never felt a difference.
So, crushed pods and stems only, no seed.
The amount of water is on you. I use like 1/3 liter or so for 15 pods. It doesn't matter (well, don't use a gallon nor a very small coffe cup, you get the picture).
Now you put that water to boil with the pods and stems.
Now it comes the only "difficult" step: you don't let it boil, you don't let it make bubles and stay like that for long. As soon as you see it wanting to boil, you take it out of the heat.
You let it repose for 20 minutes.
You drink it.
Again you are on a lot of oxy. You have 20 pods and if we attend to the 1% morphine content, if your pods are medium sized that is like 1 to 1,5 grams per pod+ stem. We would be facing at a 200-250 mg morph dose, but I would not count on it. Most comercial ornamental poppies don't reach that level, that 1% is an average, as there are some very strong comercial varieties that can yield up to 1,7%, but most of brands don't go beyond 0,4- 0,7 %.
I allways tell people to be careful, but if you are on 350 mg oxy, I can't see 20 pods harming you.
I hope you find some relief