Fishing is hilariously easy in this game, I seriously don't understand why people have such a hard time with it.

Once you get the rod and bait, you make sure you've got some stamina foods on you, go looking for a spot where you can see fish, cast into the fish, reel in to about 14 metres and wait for the bite, start reeling in immediately. Never cast into water that you can't see fish in because you will be waiting FOREVER. Fish respawn so you can come back to regular spots.