How to set a proxy server in FireFox
By default Mozilla Firefox uses the same proxy settings as set in Internet Explorer. If you wish to explicitly set the proxy server in Firefox then follow the steps below.
Start Mozilla Firefox and open Options.
Сlick on the link that says General and scroll down to Network Settings.
Сlick the Settings... button on right.
Connection Settings window is opened.
Check the box that says Manual proxy configuration and fill proxy address and port.