If you can't log in to your account first make sure you are using the correct email and password.
If you have forgotten your password then on the sign in screen, click the Forgotten Password link
Then on the next screen, enter the email address you registered with and submit by clicking the Reset Password button
You will be sent an email with a link which you can click to reset your password.
If you do not receive the password reset email, please check your junk or spam folder.