How to use proxy in Firefox
First, you must have to find a nice fast proxy to use. Below are a few sites that lists fast proxies. Use one of them, or any from your own sources ;) .
Enough? Okay, then move on to the next step.
Open your Firefox, and go to Tools > Options. Then press the Advanced button in the top. Go to the Network tab and click Settings under Connection.
Select Manual Proxy Configuration and put in the proxy IP in the HTTP Proxy text box and the port in the Port box. If you want to use poxy for other protocols then check the check box below HTTP Proxy.
Click OK. And then again click OK for the Options window. That’s it :) . Now your Firefox is in the proxy mode.