If you click on MY HOME, then account there is a link at the very bottom of the page.
Quit Membership?

Check out the information given by staff here:
http://www.chess.com/forum/view/help-support/stopping-auto-renewal-of-subscription
And the support pages:
http://support.chess.com/Knowledgebase/Article/View/168/0/how-does-membership-renewal-work
how can i quit my membership? i buy 5€ every month.