You don't need to.......It says" If yes to either question above,complete the following details"
That means you have to mark the checkbox for yes or no in both of the parts. If no to both, then dont fill extra details. If yes, then proceed to name the person who helped you. if you are using representative, you would have to fill IMM5476 form.
In your case, you have missed the tick on second part of the question and your application will be returned back.