OK, you've set your objective and met it - catch enough fish for a meal. So you've got those Blue Gills in a cooler and, well, what next? Descale and fillet, that's what's next and here's how.
Put your fish on a cutting board and stare at it with respect, the ferocious predator died that you might live. Meditation over, get a knife, a kitchen knife will do, and remove the scales; you don't want to eat them.
Next step, use a fillet knife to cut around the head, gill and fin of the fish, then work the knife along the the back of the fish, following the bones of the ribcage as a guide. When you're clear of the ribcage you'll feel it; push the knife through the fish and cut through to the tail, being sure to keep as close to the bone as possible.
That done, work the knife over the ribcage, severing the flesh from the bone. Don't be pernickity, cut the fish flesh off the ribcage when it's obvious that you'll have no more flesh. Then cut out the fillet.
Look at that small Sunfish fillet but don't be dismayed, it'll puff up several times when it's deep fried, making for a great snack.
So that's how it's done, at least in LSPland. There are different ways to do this and you can go out and do them, good luck to you, but there's no rule. At the end of the day it's all about catching your own fish, like a Sovereign, then prepping them and having a meal.