Grab your very own fishing rod from your nearest weapon store then head to the bait shop and pick up some bait. Try your luck at fishing anywhere that fish may swim! Good luck!
Go to your nearest weapon store. You can find the fishing rod under weapons then misc. You also need to go to the bait store and buy some bait.
Head to a river or creek and equip your fishing rod by opening your satchel (by pressing i for inventory), look for your fishing rod, right click on it then use. Next add your bait, look for that in your satchel and right click use that as well.
If you have done this correctly, you should see the prompt in the bottom right of your screen to prepare and cast your fishing rod (image to the left). Once you have cast, the prompts will change (image to the right)
For more detailed step by step instructions, feel free to watch the video below.