Once you arrive in Auria, you can go to the item shop and purchase a Rod1 and a Worm. With these two things, you now have the option to fish in various spots in the world. You can tell where you can fish by the little stick-like creatures in the water located in various places on the world map. Some notable places you can reach right now are: south of Drogen, northeast of Tantar, and south of Winlan.