Fishing works slightly differently from most gathering professions. In order to fish you need four things: a fishing pole equipped, training in the Fishing skill, a supply of bait (Fishing worms), and a body of water.
To fish, add the Fishing skill icon to your Utility Hotbar and click it. This changes your cursor to a targeting circle, much like with spells like fireball. Move the targeting circle over the water. A red targeting circle means fishing is not allowed on that spot. Whenever your targeting cursor is green, you can left-click on that spot to begin fishing. After you cast your line, wait for the progress bar to fill. Do not move while the progress bar is filling. Once the bar completes, you will reel in any caught fish or other items.
While you can fish and catch fish in any open water deep enough to swim within, skilled anglers can spot fishing nodes near docks and coasts. These appear as groups of ripples on the water’s surface. Fishing in these nodes can improve the quality of your catch.
Note that some nodes may be out of reach of novice anglers, and that your casting range steadily increases as your fishing skills improve. Repeated casts will deplete fishing nodes, although they will eventually restock themselves given time.
Time of day influences the chance to catch a fish. In the mornings the chance to catch fish is highest. The evening also gets a bonus to catch fish but not as great as the morning. Afternoon and night have the normal baseline fish chances.