Angling requires the presence of an [[Angling Pole]] in your inventory ([[Roshun the Traitor]] gives you one when you unlock the [[Angling]] skill), as well as bait (Roshun also sells this, but at level 15 in Angling, you can begin making your own once trained). Each bait allows for one line cast. Then you need to stand near a fishable body of water. With the [[Angling]] skill in your combat bar, select the "Angling" ability to cast your line.

Assuming it is a fish and not some other object, wait until a visual particle effect appears on you and/or on the fish. That specific particle effect is associated with one of the three angling commands: Fish Reel, Fish Juke, Fish Troll. You need to deduce through trial and error which particle effect is associated with which angling command. Each specific type of fish has its own three particle effect / angling ability associations, but they are always consistent for the same species of fish.