If you don’t know how to get the PayPal API details for integrating the PayPal with your system then simply follow the tutorial steps and you can get the details of your paypal API. this tutorial will help you to find your details.
Log in with your PayPal account.
Move your mouse over the Tools menu in the top navigation. Find More Tools within that. And click it. Scroll the page or search API credentials till you see a box with API credentials written. Click on it.
Once on the API credentials page, click on the last option for NVP/SOAP API integration.
If this is the first time you are creating API credentials, complete the API Credential Request form.
Once you’ve created the API credentials, you will see View API Signature option under NVP / SOAP API integration. Clicking on that will bring you to a page like the following screenshot. Click on each “Show” link to see the API username, password, and signature.