Definitely get in touch with someone at the school to find out whether that information is on your disciplinary file. If it is and you do not report that on your law school apps, that would be a very bad situation once the law school finds out through other means (the Dean's Cert. as jacy mentioned).
However, it sounds like it may not have been recorded (I imagine if it had been, there would have been some sanctions in addition to the F you received). Also, the school allowing you to convert the F into a W seems to suggest that it may not have gone onto your record as academic dishonesty. If, after contacting the school, you are informed there is no charge, do not include this in your apps. (Be extra thorough in your phonecalls and questions, though, because if there is record of this but you don't report it to the schools and they don't notice, you may still have trouble when it comes to applying to the bar.)
If you find out there is a charge, attach an addendum. Explain what happened and emphasize that this was a one-time thing that happened early in your college career. Accept responsibility, explain yourself, and move on - keep it short and sweet.