Hi there,
Thank you for reaching out!
I understand that you’d like to connect your WooCommerce store to POSTMAN
payment gateway.
The only Postman I’m familiar with is a tool for developers:
https://www.postman.com/
https://d.pr/i/doyUIY
Perhaps you could link to the payment gateway you have in mind here?
If it is a payment gateway that doesn’t yet have a WooCommerce plugin and you want to write a new one to connect your site to that payment gateway – this will not be an easy task, but this support document explains the basics:
https://docs.woocommerce.com/document/payment-gateway-api/
I will not be able to guide you through this step by step since I have not written any payment gateway plugins myself. If you need step by step instructions – you might be better off just using a different payment gateway which already has a WooCommerce plugin written for it.
If you decide to still write your own plugin though – this article has the step by step instructions for plugin developers:
https://rudrastyh.com/woocommerce/payment-gateway-plugin.html
I hope this helps!