Put the email associated with your account into the field and press "Send Reset Password Request".
That email address will receive an email from Plan to Eat <firstname.lastname@example.org> with the subject line Reset your password. Many times these reset password emails end up in spam boxes. If you don't receive the email, go look for it in your spam filter. If you are using Google, Hotmail, Yahoo, or other big email services, you may have to actually log into the web interface for your email and check your spam filter there.
In that email is a link to "Click here to reset your password". When you press that link you will be taken to a page where you can type in a new password.