To generate an API Signature, you need to have a verified PayPal Business account. If you're testing with a Sandbox test account, repeat these steps for your Sandbox test accounts and your live accounts. We recommend having WordPad open and using a separate web browser to perform these steps. If you do not open WordPad, at least have a pen and paper ready to write down the information.
1. Go to the PayPal website and log in to your account.
2. Click on your account name at the top of the page and select Account Settings.
3. Click on the Update option for "API access" in the Account Information column.
4. Scroll down to NVP/SOAP API Integration (Classic) and click Manage API credentials
5. On the next page, ensure that Request API signature is slected and click on Agree and Submit.

6. You should be taken to View or Remove API Signature. You'll need to click on Show for the API Username, the API Password and the Signature. Copy all three of these results.

Now that you have this information, navigate to the appropriate payment gateway information and populate it.
- In Enterprise (the web), navigate to System Management | System | Payment Gateways.
- Add and set the new option Gateway to PayPal.
- Login is your API Username.
- Password is your API Password.
- API Signature is your Signature.
- Attempting to set this up in Enterprise for Windows is not supported.