The Klarna Checkout module for PrestaShop can be downloaded from here.
Once installed and activated, the module's settings can be found by selecting Configure next to the Klarna Checkout module in your store's Module Manager.
An SSL certificate is required for the Klarna Checkout (KCO) module.
The below settings will show you how to offer Klarna at checkout to your customers.
On the Klarna Checkout V3 tab, ensure the Activate KCO V3 setting is toggled on once you are ready to have Klarna live on your site.
Klarna API Username/Password
You can generate your Klarna API credentials in the Settings app of the Klarna Merchant Portal. These will consist of a username and password.
On the Common Settings tab, testdrive allows you to test your integration to ensure it is working properly before taking real orders. Orders placed while in test mode will not cause any real money to be exchanged. Moving the switch next to No enables live (production) mode and orders that are placed in live mode are real, valid orders. You can sign up for test credentials here.
Activate order status and Cancel reservation status make use of the Klarna Order Management API. Once an order status is selected here, when an order is given that status the corresponding action will be taken on the Klarna order.
Make sure you click Save at the bottom of the page when you are finished.