BankID on file consists of data which is stored on the hard disk of your computer. You activate BankID on file at your Internet bank.
When activate BankID on file you also choose a personal password which is linked to your BankID. Nobody else besides you knows this password. The bank does not either know the password and therefore the password cannot be reset if you forget it. If you forget your password, you must activate a new BankID at your Internet bank.
If you write down your password, make sure that you store it in a safe manner so that nobody can gain unauthorised access to the password.