You click on the downvote arrow. However, you need to have sufficient karma for the downvote arrow to appear. You do not appear to have passed this threshold yet.

Also, if this was not a honest question but just a rethorical one: please read and take to heart the HN guidelines [1]. Essential part: It is better to explain why you disagree with the parent poster than to post snarky comments that do not contribute to the discussion.

[1] https://news.ycombinator.com/newsguidelines.html