First you will need to gut it!
Here's how:
First you will need a sharp knife and a teaspoon...
and some nice, freshly caught fish!
Wash the fish in cold water and then turn the fish over and insert you knife right about here!
Make a slit below the skin right up between the fins to the gills.
Cut the small bridge of bone at the head between the gills.
Carefully pull out the innards from the head downwards towards the tail.
Slice the membrane down the length of the fish.
Scoop out the yucky stuff with a teaspoon and give the inside a good wash in cold water.