tu go to Fanpop's inicial page. Then tu click on the category that the club is in (device sideways: go to the bar at the parte superior, arriba above all of the featured content. Device vertical: scroll all the way down to "browse clubs") and find the club. And then tu click the red x that says "leave".
Go to your perfil and go to the section clubes (fourth grey button beneath the banner). Find the club tu want to leave. Hover on the top-right corner of the club's box and a cruzar, cruz will appear. Click on that cross.