Add enough boiling water to make 400 mL (or as directed in the package).
Pour over the oats.
Cook in microwave for 1-2 minutes. Cook time depends on the type of oats used, how thick you want your porridge to be, and also the microwave power. I usually used rolled oats and cook it for 1 1/2 minutes.
I usually do not add milk when serving, unless I overcook the porridge and it becomes too thick :D.