PayPal payment gateway
PayPal integration is included by default with the software.
Name allows you to specify whatever name you like for this payment gateway.
Live email address is your primary PayPal email address.
Developer mode can be enabled if you would like to run test payments in your PayPal sandbox account. If developer mode is enabled you must fill in related developer email address and optionally your developer API details.
API username, API Password and API signature can be obtained in your PayPal account. To do that login to your PayPal account and click on "seller preferences" under "selling tools".
Click on "update" next to "API access".
Click on "Request API credentials".
Make sure "Request API signature" is selected and click on "Agree and submit".
Copy API details to PayPal gateway settings in the control panel and click on "Done".