Clue:
You can purchase the eye of newt at the Port Sarim Magic Shop. Speak with Betty. Next go kill a cow or a bear and get some meat. Use it on the range. If it doesn't burn use it on the range again. Next you will need to get a Onion. You can find the onion field a little North of Rimmington, all you need to do is just pick one up.
The last thing you will need, is to get a Rat's Tail. You can get one by going back to the starting point and searching for a rat in one of the near by houses. Now that you have all of the items, bring them back to Hetty. She'll tell you to drink from the Cauldron. Drink from it. You have now Completed The Witch's Potion Quest!
