Firefox maintains its proxy configuration in a profile. You can preset the proxy in a profile and use that Firefox Profile. so i think u have to change ur existing firefox profile. U will found a lots of resource how to change FF profile for proxy. – noor Jul 11 '16 at 10:35
Setting up a proxy server in Firefox If you want to connect to Firefox with a proxy, then the good news is, Firefox is a highly flexible browser that allows you to do just about anything in it. Sure, it has some trade offs but browsing with a proxy is one of the most secure ways to browse the internet. How to set up SOCKS5 Proxy on Firefox | CactusVPN If you still want to use the FoxyProxy add-on to set up SOCKS5 proxy in Firefox, just follow the steps below. Part I. Install FoxyProxy Open the Firefox menu (1). and click on “Add-ons” (2). Go to “Extensions” (3) and search for “foxyproxy” (4). Set Proxy for Browsers - Free Proxy Blog Aug 14, 2007 Configuring Firefox to work with Burp - PortSwigger
How to set Socks5 proxy at firefox browser - YouTube
If you still want to use the FoxyProxy add-on to set up SOCKS5 proxy in Firefox, just follow the steps below. Part I. Install FoxyProxy Open the Firefox menu (1). and click on “Add-ons” (2). Go to “Extensions” (3) and search for “foxyproxy” (4). Set Proxy for Browsers - Free Proxy Blog Aug 14, 2007 Configuring Firefox to work with Burp - PortSwigger
Aug 08, 2018
How to configure Proxy Settings in Mozilla Firefox - YouTube