Simple. Bring a knife, attack potion (2), and 40 feathers. Teleport to the Barbarian Outpost using the games necklace. Go south, and when you reach the whirlpool near the waterfall, go west. Then south. You should reach a little house which has Otto Godblessed in it. Talk to him concerning the fishing topic. You need to do the fishing part before you can proceed to herblore. You're supposed to get the fishing rod from him, or under his bed. Go to the nearby lake and go to the fishing spot. You'll start fishing. He wants you to catch one of the leaping fish. Once you've caught one, use your knife on it and hopefully you'll get fish offcuts and roe. The offcuts are inedible, and are used as bait for the leaping fish. If you have feathers, however, you'll use feathers before offcuts. The roe is used for barbarian herblore. It's used for low leveled potions. It comes from leaping trout and leaping salmon. Caviar is for high leveled potions, and comes from leaping sturgeons. You can only use the fish eggs on potions with two doses. Put the roe into the attack potion (2) and give it to Otto. Done. I hope I didn't leave anything out, and I think this has answered your question.