Hi,

You can have a look at this existing question:  Documentation for Payment Acquirer development

For the payment acquires the steps will vary from one payment acquirer to the other, in the case of the adding new payment acquirer, collect the API documentation from the provider and follow the steps they have specified, to integrate it in odoo, you can check and see how the default payment acquirer module is created.

In odoo itself, by default there is different acquirers available like stripe, paypal etc, just see how it is coded and also you can have a look at the other payment acquirer modules available in the odoo apps store also.

Thanks