Be logged in. Top right (under your name), go to Settings. On your right hand you’ll see the deletion link.
Be aware: Any of your ideas that others have voted on will be attributed to “Anonymous”. All of your ideas without votes and all comments will be deleted. So you may want to try and delete/anonymise contributions first, as far as you think this is necessary.
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.