There are many reasons why one might need to configure/change the proxy settings of one's browser. One of those reasons is to bypass a network's firewall to enjoy some certain benefits e.g. using the blackberry plan of MTN Nigeria to browse on computer;
you can check my previous post on how to do that.
We will go straight to the matter and learn how to do that here on this post.
Please, note that I used Opera version 12.17 and all screenshots were derived from that version. Hence, the arrangement of options or view may differ from yours.
Step 1: Click 'Tools' in the menu bar. Next click 'Preferences'. See pix below for reference.
or press 'Alt+P' keys on your keyboard.
Step 2: Click 'Advanced', Next click 'Network, then click 'proxy servers'. See attached pix below:
Step 3: In the next window that opens, click 'use manual proxy configuration' and enter your desired configuration settings. See pix below as usual
Good luck to you all.