Note: We are using Firefox 36.0.1 to demonstrate the changes, but these steps should be similar for all versions of Firefox.
Open the Firefox menu in the top right corner and click on 'Options'.
Next, click on 'Advanced' in the top right corner, and then the 'Network' tab.
In the 'Network' tab, click on 'Settings'.
This will display the Proxy Connection Settings window.
In 'Connection Settings' click on 'Manual proxy configuration'.
In the HTTP Proxy field, enter the SHP hostname or IP address of your Proxy Server, and the Port Number in the Port field.
Press OK and OK again to save your settings.
Now when you surf, you will be surfing through the Proxy Server. The first time you surf, depending on your account's authentication settings, you may be asked to enter your credentials, which were supplied in your Welcome Email.
To stop using the Proxy Server, repeat the above steps, but select "No Proxy" on the Proxy Connection Settings window.