1. Log on to the computer on which the
configuration is to be made.


2. Ensure that Mozilla Firefox is successfully
installed and is running seamlessly.


3. Double-click the icon of Mozilla Firefox to
initiate the web browser.


4. On the top left corner of the opened
FIREFOX interface, click the Firefox button.


5. On the displayed menu, go to Options >
Options .


6. On the opened Options box, click to select
the ADVANCED ICON


7. On the Advanced interface, go to the
Network tab .


8. Under the Connection section, click the
Settings button.


9. On the opened Connection Settings box,
click
to select the Manual proxy configuration
radio button.

Read more: http://gossipzone./configure-proxy-settings-in-mozilla-fire.xhtml

thanks bro lets see if it works