You can do basic fishing with any fishing rod and Bait Worms.
Just find a spot near water and Shift Right Click on the Fishing icon on your toolbar to continuously fish for as long as you have Bait Worms in your inventory.
So far, I have learnt of 2 methods to get started on Fishing. Please read below to see which one is for you!
Method 1 - Recommended for Experts
Method 2 - Recommended for Beginners. The quests explain mechanics of fishing!
Method 1 (Expert)
Craft a rowboat. This gives you a basic fishing rod.
This uses 10 Lumber + 5 Labor at a Carpentry Workbench.
Grab the Hero Hall statue buff for +2000 proficiency buff.
You will need 2000 Leatherwork to do the next step.
Upgrade your Dawnsdrop Boots to Dewy Dawnsdrop Boots.
You get the whole set of Dawnsdrop gear when you finish your Blue Salt Brotherhood questline.
1 Dawnsdrop Boots + 8 Moonlight Crystals + 10 Eel + 110 Handicraft Yarn
Upgrade your Basic Fishing Rod to Novice's Sturdy Fishing Rod.
1 Basic Fishing Rod + 1 Crafted Fishing Hook + 1 Basic Fishing Line + 1 Sturdy Steel Reel + 2 Opaque Polish
If you are crafting a Crafted Fishing Hook, you can find Regal Handicraft Desk in starter areas.
Craft Sports Fishing Lure.
15 iron ingots + 10 Labor (Handicraft Kiln)
You do not need to get it to 100% at Divine.
Method 2 (Beginner)
Talk to Fisherman Santiago in Seachild Wharf, Cinderstone Moor or Fisherman Riko in Caernord, Ynystere.
Simply follow the questline.
The quests explain how fishing works in the game!
You can either fish or buy these sea creatures from the Auction House. Check the climate if you are going to fish for them!
Finally, find a fishing raid & fish using the new boots & fishing rod!
You only need to finish this last quest if you want a +1000 fishing proficiency title, Discriminating Tastes.
If you see School of Fish, chum the area.
When it turns into Fish Feeding Frenzy, you can throw your lure in & wait for a bite!
Pay attention to the buffs under the fish. Follow it using your fishing rod skills.
Gotta be fast! Good luck!