There are two ways that VPOP3 can be configured to connect to the Internet. Which one you use depends on the service provided by your ISP.
This is the most common connection method. It assumes you are connecting to the Internet via a router which is permanently connected. In this scenario VPOP3 simply needs to connect to the router so setting up VPOP3 is very simple.
All you need to do is go to the Connection tab in the VPOP3 settings, add a connection and choose Use LAN for Connection.
You do not need to tell VPOP3 the IP address of the router or anything like that. This should all be set up in the Windows TCP/IP settings, exactly the same as for other computers on the network (ie you should set the DNS settings and the Default Gateway settings appropriately)