How do you fish on Animal Crossing DS

You need a fishing rod from Tom Nook's store. Then go to the seaside and in the item menu (Y) drag the rod onto your body. You should see yourself with a rod. Look for a shadow of a fish and while facing the water and the fish shadow tap your head. When the red and yellow part goes under the water tap your head ASAP. You can sell fish or display it at your house.