Once you arrive at the Sign In screen, you will be prompted to enter a Customer Id or Username, and a Password. If you have signed into your account after 10.19.2015, you would have been prompted to create a new Username and Password. If you have not accessed your account after that date, you will need to enter your Customer ID and Password and click on Sign In.
You may use the Forgot Username and/or Forgot Password links on the sign in page to retrieve either a Customer Id or Username, and to reset the Password. If you have not yet created a Username, know your Customer Id but not the password, after clicking the Forgot Password link choose the Forgot Customer ID Password link in the next window.