How to add a payment method

[Roby-Wan-Kenobi]

"require": { "php": ">=7.2.9", "october/rain": "^2.0", "laravel/framework": "^6.0", "october/system": "^2.0", "october/backend": "^2.0", "october/cms": "^2.0", "october/media": "^2.0", "october/editor": "^2.0", "rainlab/blog-plugin": "^1.5", "rainlab/builder-plugin": "^1.0", "lovata/shopaholic-plugin": "^1.30", "lovata/toolbox-plugin": "^1.33", "lovata/ordersshopaholic-plugin": "^1.29", "league/omnipay": "^3.1", "omnipay/stripe": "^3.1", "ignited/laravel-omnipay": "^3.3", "lovata/omnipayshopaholic-plugin": "^1.7" },

I followed all the instructions, installed all the required libraries but I don't get how to implement a real payment method, for example stripe.
In the documentation you say "Extend PaymentMethod model form." where is it? How do I add a payment gateway? Is there a tutorial somewhere?

By the way after I have installed all the packages I'm not able to publish the laravel-omnipay config. It's not in the list of the vendor configs