Your username is your email to which you have received the invitation email. Type it and click on "Continue"
Type in your created password to login to the portal. If your organization email is also used by other organizations, the portal will need you to insert the Organization Code that you received in the original invitation email.
To retrieve your forgotten password, click on "Forgot your password?" which will ask you to type your email in order to send you a link to reset your password.