Be logged in, click the link, where you'll clearly see the deletion link.
Enlace de la terminación directa: http://twitterfeed.com/account
Publicly visible text/images often aren't properly deleted even when you succeed in deleting an account. Try editing or deleting them manually before deleting the account itself. If you're unsure what happens to your tracks you can always contact Twitterfeed and ask personally. By the way, deletion requests don't necessarily mean your data will actually be deleted (e.g. due to legal obligations).
If you signed up for Twitterfeed using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Twitterfeed. Click the icon below to find out how.