So, how do I use this thing?

Glad you asked. There are two main things you need to do before you can fish successfully.

Choose a good "Bobber Color". The "Bobber Color" is the color used to identify the fishing bobber on the screen. GoneFishing will scan the WoW window for this color, so you must ensure that it is accurate!

Navigate to the "Bobber" tab in the Preferences window, where you will see a "Bobber scan color" option with a color well next to it. Click the color well to bring up the color selection window.

The best way to choose the correct color is to click the magnifying glass icon and use it to choose a color from the screen. The red feather on the bobber is often the best, most distinguishable color to choose. So open WoW, manually cast your line, and then choose the color from the bobber itself. Once you have set your color, you may close the color selection window.

Set your Fishing hotkey. This is the WoW key combination that will be pressed to make your character fish. It should be bound to your fishing ability in WoW.

Click the "Hotkeys" tab in the Preferences window. The first hotkey at the top, titled "Fishing ability hotkey", should be set to whatever hotkey you use to cast in WoW. Enter the key to press in the text field here. If you use the default value of "1", that means your fishing ability should be in the "1" spot on your hotbar in WoW. GoneFishing will simulate this hotkey when it expects you to cast.

Please note! GoneFishing will not fish while the preferences window remains open!

Add the fishing ability to a hotbar somewhere and make sure it is bound to the same key-combination you entered in the preferences.
Turn on Auto-Loot from the "Interface Options" window. This allows you to easily loot any fish you catch.
It helps a lot to disable "Click to Move" (if you use it). Click to move often results in your character dead underwater after a false-positive...
Turn your graphics up as far as you can, especially full screen glow. Higher graphics makes on-screen colors more vivid, helping to identify your bobber.
Find a good spot to fish, and zoom your camera all the way in until you are in first person view. Make sure your character isn't obscuring any part of the screen.

You are now ready to fish!

GoneFishing