Need add extra payment methods


I want to add debit card payment method also where can i add it


Either use seed data (we got an example in our demo data for you), or use the user interface: Catalog Manager > Product Stores > Your Store > Payment Method (in action menu).

If the payment method is missing from the dropdown, you will need to add it to the seed data, and possibly implement the functionality for it to be handled correctly. In case of debit card payments, most likely you will rely on an external payment provider for it all. Have a look at the credit card implementation for one of the existing payment gateways to get an idea on how it was done there.