Go to your store dashboard then click on Payment

Toggle on the Online Payment
Click on Settings
Click on Add payment provider
Choose Amazon payment services (If it doesn't appear, click on view all)
In the summary, You'll find the supported countries and cards, then Integrate
These are the requirements ( PayFort Access code - PayFort merchant identifier - PayFort SHARequest phrase - PayFort SHAResponse phrase)
Create your account on Amazon
Go to Integration settings --> security settings
Copy the following info to be pasted in your store
**Make sure to choose SHA- 256 in SHA Type **
Make sure to choose the same currency chosen in your payFort account
Go back to your store, activate the buttons
Paste the info you copied, then Next
Activate the buttons, then Finish