Pretty self-explanatory. Just make sure you have a positive amount of money going in to the Final Jeopardy! round. (Otherwise, if you have $0 or a negative amount, you won't be able to participate in the round.) Then, when it comes time to wager for Final Jeopardy! just choose $0.
If you are playing single player, you will be able to pause the game once the question is read. That way if you don't know the answer yourself, you can simply Google it to ensure you have the right answer. Answer it, and you will win $0 and this achievement!