Are you referring to the Owners Directory, or the Owner Reviews? I think the Owners Directory listing is automatic, in other words, when you signed up as a user on this forum and listed what you have for a boat, it listed you under O'DAY 240 owners. If you did not specify a boat model when you signed up, then I think you can edit your profile to add the boat model.
If you are referring to the "Owners Reviews", then there is a link on the 240 Reviews page to enter your review.