Your email address is your username and you should use that when logging in.
If you have forgotten your password, use the 'Forgotten your password?' option to request a link to be sent to your email address to enable you to reset your password and login. This can be found when you select the 'Need help signing in' option at the bottom of the Login page. Once selected it will show the 'forgotten your password' option:
If you no longer have access to the email address that is in your login, please contact The Hundred customer support team, who will update your account for you. Click Here