How do you make fried catfish without the gritty cornmeal texture?

To say the same thing as everyone else, but in "layman's terms" since you said yourself that you "don't know anything about cooking" ... you want to look for "New Orleans Style" fish fry ... it's made with the aforementioned corn FLOUR as opposed to corn MEAL.

If using Louisiana Fish Fry Brand, it's in a yellow bag, and actually labeled "New Orleans Style with Lemon" ... if using Zatarains' it's the same thing ... corn flour.

There's also a product called cream meal that is a very fine ground meal. It is excellent on fish!