To setup paypal express checkout:
Login into your paypal business account.
Click the following link for a shortcut to your API credentials:
https://www.paypal.com/businessprofile/mytools/apiaccess/firstparty/signature
Then login to your website's admin area and go to:
1. Modules > payment
2. Remove the paypal standard payment module.
3. Install the paypal express payment module.
4. Enter your paypal API credentials.
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To find your API credentials in your paypal account (instead of using the shortcut above), login to your PayPal account and go to:
1. Tools > Business setup.
2. Offer PayPal checkout on your website > setup online payments.
3. Choose option B.
4. Setup API access when you're ready to go live.
5. Find 'NVP/SOAP API integration (Classic)' > Manage API credentials
6. Click 'show' and copy the API credentials
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