1. Click "Open menu", in the upper right corner of the browser window, the three horizontal stripes icon. Select the "Settings" section from the list.
2. Scroll down the menu. In the "Network Settings" section, click "Configure".
3. In the "Connection Settings" window that appears, check the "manual proxy setting" window. To turn off the proxy you need to check the "without proxy". In the "HTTP Proxy" line, you need to specify the IP address in the port section of the proxy port. Below to put a tick on "also use this proxy for FTP and HTTPS". Configuring a proxy in Mozilla Firefox is finished.