The fishing system in 2Moons is not very complex but it's amusing none-the-less. Fishing in 2Moons is basically a mini-game that allows you to obtain usable items like hp/mp potions and jewelry. The ability to fish is also a skill point trade-off in that you have to spend skill points on the ability.

First you have to get the skill and level it to the required level. Water around starter town will be level one and as you start to move into higher level areas like Parka Shrine level 2 will be required and so on.

You can buy a rod from venders in Loa Castle and Braikken Castle and there are level requirements for every available rod, the first rod requires level 7. You can also buy bait that increases you chance of success.

To fish you find appropriate water and hit "L", this brings up your hook icon. Now click the hook where you want to fish and hold left-click when you get a fish on. That's about it. You will catch different fish that can be redeemed for potions and consumables and jewelry. I put in a couple fishing sessions at Parka just to try it out and I caught a couple pieces of decent jewelry in a few hours.