NetWorx can only monitor traffic on the computer where it is installed. So you basically have got two options:
1. Install NetWorx on every computer on your network. This can only be done if all your computers are running Windows. While NetWorx can only monitor traffic on the computer where it is installed, instances of NetWorx can talk to each other so that each instance is synchronised and shows the actual overall usage. In this case gaming consoles, mobile phones, etc will not be metered.
If you choose this way, the synchronisation needs to be turned on on all the computers in the
advanced settings.
2. If your router supports so-called SNMP or UPnP protocol, you can monitor all traffic via your router. This however will not give you a per-computer usage breakdown and the monitoring computer must be continuously on to poll the router and collect usage data. Check your router's documentation with regards to the SNMP support.
Unfortunately there isn't an easy way to monitor per device usage for all devices. This is only possible when you have a specialised server between your router and the rest of the network, which is not feasible for a small home network.