How about mentioning or working it in the essays/short answers? Let’s say the prompt is, “What did you do last Wednesday?” You could respond as, “I was elated when notified that I am published in the letter-to-editor section of the NY Times; however, it still did not compare with the joy I felt for Johnny, whom I tutored in math and he got an A- on his latest math test.”
Added in edit: OP, having been published in the NYT is an accomplishment of yours, no less.