Here are the steps that you need to follow in order to get your REST API application created for PrestaShop
1. Access https://developer.paypal.com/developer/applications/ 2. Log in or Create a business account 3. Inside Dashboard left navigation menu, click on My Apps & Credentials 4. Under REST API apps, click on “Create App” 5. Add as an App Name “PrestaShop” 6 Choose your default “Sandbox developer account” 7. Your Sandbox Client ID will be shown. Click on « Show » below « Secret: » in order to display “Secret” key 8. Copy/paste your « Client ID » and « Secret » on PrestaShop window for each environment To get your Live credentials, switch on top right Live toggle and repeat the 2 last steps