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 "Profile" at the top of the page.
3. Click "API Access" in the Account Information column.
4. Click "Request API credentials."
5. Select "Request API signature".
6. You may receive an additional screen prompting you to give 3rd party permission or to view - click on "View".
7. Click "Agree and Submit."
8. Click "Done."
9. Open WordPad now.
10. Highlight and copy the API User Name, Password, and Signature; paste them into WordPad.
11. We also recommend capturing a screenshot of the browser window by using Alt+PrtScr and pasting it into your word processor.
These last steps are important so you have a backup of your API credentials and you can copy and paste them into Enterprise instead of typing them in. If they are not entered correctly, PayPal will not interface with your website.