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