How do I integrate a custom payment app in Shopify?

[darshi_gilder1]

I want to create a custom app payment gateway integration APP in shopify. I've read some articles in the official shopify documents. But, still confused about the steps. Firstly, I've to create a public app using laravel/ossiset package. But, after installation it provides API & Secret settings in backend. But, if I want to add it in the payment provider section how can I do? In one article it shows "Give your payments app extension a name" in the payment tab. But, I don't find anything like it. Also, I'm totally confused in the flow. Can anyone please guide me?

Thanks in advance!
Looking forward to your response.

[darshi_gilder1]

If you've experienced developers in your company then please tell them to guide me in this.
Thank you for the reply.