It depends on the software you use and for what you use it. If Networks is an application that's used to monitor and manage networks components, traffic, statistics, then you should access one of its modules called Stats or Statistics. On that page there should be a string to indicate the total amount of traffic. The downloads traffic is considered as Traffic Inbound (comes from an exterior source). That's the one you need to check.
If you see the software is too complicated to be used, then install BWMeter and it should tell you in real time with graphics the total download for the current session.