WAN interface configuration

[Balanga]

I'm finding it difficult to work out how to configure the WAN interface for accessing the Internet. I'm using a Virgin Media hub configured in modem mode, but have no idea how to assign the IP address for the interface.

As a first step to getting things working I installed a LinkSys router, with DD-WRT installed, between the hub and my switch to see if there would be any problems using the hub as a router. To my surprise everything just worked without any need for configuration.

I was hoping to just replace the LinkSys router with my pfSense box but apart from accessing the Web configurator from another system I couldn't  get anything working, and lost Internet access for a couple of hours until I managed to get everything back to its former state?

Just so that I can get used to using pfSense, can I plug it into my network just as a DHCP server?