How to Use PayPal API

1. Enter your PayPal Business account username and password at PayPal.com and select the "My Account" tab. Click the "Profile" link and choose "My Selling Tools." Click the "Update" link in the "API Access" row. An API Access page appears.
2. Request API credentials for your own use by clicking the "View API Signature" link. This option enables you to get the credentials necessary for customizing your website with a PayPal API. It also enables you to use preintegrated shopping carts that run on your own server.
3. Copy the API Username, password and signature fields. Paste theses PayPal API credentials into a document for safekeeping. This is the information you need for configuring a preconfigured shopping cart or building a custom shopping cart yourself. Keep your credential information secure. Do not share your API username, password or signature with anyone.