To start fishing you need to position character in front of a water. Find a position where water is located from the east, as this is default camera direction of a character after login:

If you use ship, stand in the center of a ship. Fishing from a ship is recommended, as bot may use ship's inventory to take fishing food, beer or new rods from a ship. If overload detected, bot may also unload dried fish to your ship. To unload dried fish to your ship, drop one piece of a dried fish of each type to ship's inventory. Bot will scan dried fish types by icons and find the same types of a fish in inventory to unload:

Update: using mount inventory was disabled after 24.10.2018 BDO patch
You can use any types of a fishing rods. Basic rods may be purchased from NPCs. As a rule NPCs with   or  icons on the map may sell you basic rods. Other rods may be purchased from auctioneer . green thick fishing rod may be also purchased from pearl shop (F3) for 25 loyalty points.

Use fishing tab to specify parameters of a fishing (resize window with mouse if necessary to see all controls):

IMPORTANT NOTICE: bot does not distribute between multiple types of a fresh fish by images, but detects image of a timer common to every fresh fish. A few items in black desert online have timers also: e.g. boss scrolls or lantern (before it was removed from the game):    Remove such items from character inventory or bot may trash them as a fish.

To start fishing select fishing algorithm from drop down menu on the front page of the bot and click START button: