Summarize this article:

Cover both sides of the fish with seasoning. You can add a splash of olive oil to the exterior of the fish before adding your spices to help the seasonings stick. After adding the spices, place your fish directly in the hot skillet. Blackening fish in a skillet takes a little longer than grilling because of the reduced temperature of the stove. Keep your stove on medium-high and flip the fish fillets halfway through. Reduce the heat to medium-low for the last 2-3 minutes. Your meat will be done when the edges have blackened, and the fillet has a smoky color. The meat should be easy to pull apart with a fork. Refrigerate any leftovers in an airtight container for 2-3 days.  You can also freeze any leftovers in an airtight container or bag for up to a month. Use a meat thermometer to make sure that the inside of the fish has reached at least 145 °F (63 °C) if you are unsure if it is done.

Summary:
Sprinkle the fish with salt and ½ to 1 tsp (1 to 2 grams) of seasoning. Place the fish in the skillet for 5-6 minutes. Serve your fish immediately and store leftovers in the fridge.