Sometime we may need to connect to a web service that, for security reasons, accepts incoming connections only from specific hosts or IP addresses and our computer does not match any of those requirements.
The best way to connect to those services is to connect first to an intermediate computer that act as proxy to the target service we want to access.
To configure Mozilla Firefox to access a proxy, you first need to have the proxy details (you may request them to the Network Admin of the service you need to access):