You'll need to create an API username for PayPal that's different from your shopping cart's username. You can access PayPal via API only if you have a PayPal Premier / Business / Website Payments Pro account.
Follow these steps:
- Log in to your PayPal Business account.
- Click the My Account tab.
- Click the Profile tab. If you haven't already done so, you need to verify your account before requesting API credentials.
- Click Request API credentials under Account information.
- Click Set up PayPal API credentials and permissions under Option 1.
- Click Request API Credentials.
- Click Request API signature.
- Click Agree and Submit.
- Copy and paste the API username, password, and signature into your shopping cart's configuration or administration screen.