Add your payment page to Shopify site

I have recently taken over a Shopify web site for a C# Visual Studio application I created for a client. We have a LimeLM license for the product and I am integrating that into my C# project. Now I need to add the checkout/payment page to his Shopify site using the C# examples in your API package. How do I integrate your page with the Shopify site? Do you have docs on this? Also, we will be adding SaaS product to the site shortly. Do I need to create a non-Shopify site to have more control? Suggestions?

I ran across this Shopify App installation video, but don't know where to get the app or how to add it to the Shopify site and exactly what it would do for me.

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We do not offer an integration for Shopify. That video you linked to is created by a third party and we've asked them to remove it for trademark infringement.

Use any of the available payment platform listed here: https://wyday.com/limelm/help/how-to-generate-product-keys-after-order/