Configure Proxy Listener

1. Start Burp Suite.

Go to 'Proxy' tab > 'Options' sub-tab > 'Proxy Listeners' section, and validate the proxy listener settings. It should be same as that set in the Firefox browser, i.e., enable a proxy listener for localhost (127.0.0.1) on port 8080.

Switch to your Firefox browser and navigate to www.example.com

Switch back to Burp and navigate to the "Intercept" tab.

Forward the intercepted request.