To integrate the payment method PayPal you need a PayPal account with API access.
Auf der "My Profile"-page at PayPal there is a point "Seller/Dealer". There you can manage the API access.
The Smake system uses the NVP/SOAP API integration (classic).
There you will find the required data:
- API username
- API password
You can simply copy this data to your backend.
Of course you can still use all other payment methods like Stripe, Invoice & Co.