It is showing I have already registered whenever I try to register as transporter , what is this indication ?

This indicates that you have already registered on the eway bill portal. You will need to provide your PAN, business details, and create your username and password. These details will be required to log in to the e-way billing system. Forgot your password or username? Then please use the "Forgot Username" or "Forgot Password" facility on the portal to retrieve it or create a new password.