Here are the steps you take to set up Paypal Payments Pro on IXXO Cart 

1. Login into PayPal account 
2. Go to Profile 
3. Choose API Access under Account Information 
4. Request an API certificate 
5. Fill in the form. On this form you will see API Account Name and Password- An API Account Name and password are required for certificate usage. The following API Account Name has been generated for you. Please specify a password. For security reasons, it should not be the same as your PayPal password. Paypal generates Account Name automatically, but password is provided by user. These username and password have to be entered on PayPal Pro settings page in admin area. 
6. Click Continue button 
7. You'll see API Certificate Request Review form 
8. Review it and click Generate Certificate 
9. Download certificate 
10. Authorize just created API Account Name – copy / paste it into API Account Name text area and check all checkboxes; Save changes. 
11. Rename certificate file to “certificate.pem” 
12. Upload your certificate to content/engine/payment/paypal/ folder on your server (where IXXO PHP Shopping Cart is installed) 
13. Go to admin area and complete setup.