PayPal has specially designed a new payment gateway for mobile. PayPal Mobile supports credit and debit card payments. PayPal email, Client ID, Client Secret, API Username, API Password and Signature are required to integrate this payment gateway to your App.
Go to https://developer.paypal.com/ and log in to Developer website using your PayPal account by clicking on the Log into Dashboard button at the top right of the page.
In My Apps & Credentials, click on Create App button.
On Create New App page, enter your App Name then click on Create App.
After that, you will see the REST API Credentials for Sandbox mode and Live mode.
You can switch between Sandbox and Live by click on the button at the top right corner.
Sandbox means that all transaction information is sent to test servers at PayPal. No money trades hands in test transactions.
Live means that all transactions that you have submitted are sent to the financial institutions for processing and that real money is transferred.
Click Show to see Secret Key.