PayPal Payment Gateway Setup
Log in to your PayPal business account at www.paypal.com. Click the profile icon 
on the top right side of the page. From the Business Profile menu, select Profile and Settings. 
From the left menu, click My selling tools. In the Selling online section, click the Update link for the API access item.
To generate the API signature, click Request API Credentials on the API Access page.
Go to the top level menu your name.currinda.com account
In Misc. settings > Payment Gateways > select PayPal Express in type field and name the Payment Gatewayfor reference. 
Add in the Login, Password and Signature as obtained from PayPal in step 4. Click on save. In your Organisation or Event > Setup > Financial >Payment gatewaySelect the name of the payment gateway setup in step 5. Click on Save.