The PACER login page has a link to help you reset a PACER username or password.

To reset a username, you must know your PACER billing email address and either your account number or your first and last name and date of birth.  To reset a password, you must know your PACER billing email address and either your account number, your username, or your date of birth.  

You will receive an email prompting you to answer the security questions you entered when you created or updated your PACER account.  When you have successfully answered those questions, you will be prompted to reset your password.

If you are trying to link your PACER account to your ECF account so you can efile, and you have forgotten your ECF login or password, contact the court.