To set up Merchium with PayPal Website Express account:
  1. In the administration panel, go to Administration > Payment methods.
  2. Click the + button on the left.
  3. Enter PayPal Express into the Name text input field, select PayPal Express Checkout in the Processor drop-down select box, enter necessary description or surcharge values  into the appropriate input fields, upload an image if needed.
  4. Open the Configure tab in the same window in order to view the PayPal Express settings section.
  5. Fill in the following fields:
    • Username - your PayPal Express API username
    • Password - your PayPal Express API password
    • PayPal authentication method - select the desired authentication method
      • If you selected Certificate, upload a certificate file.
      • If you selected Signature, fill in the Signature field - enter your signature (you can find it on the API Access page of your personal account at http://www.paypal.com web site)
    • Send customer shipping address - select this check box if you want to send the customer shipping address to PayPal.
    • Currency - select your currency
    • Test/Live mode - select Live mode. In order to use Test mode you need to get additional accounts at PayPal Sandbox.
    • Order prefix - any prefix you want orders to have (optional field)
  6. Click the Create button to save the changes.