Here I bring you the necessary files that are included in the extended license of Stackposts to have enabled the payment system for your users.
With this you can configure and enable: Paypal and Stripe.
These files come officially with the extended license that costs $380.
You just have to upload the app folder to your server via FTP.
Once loaded, you must already appear all the options related to the sales system on your site.
You have all the documentation of how Paypal, Stripe and pagseguro is configured on the official Stackposts website.