Newbie build advice please

[pompeyrodney]

Hi
As a newbie who wants to further his understanding of networking and routing particularly, I have installed PfSense on an old Dell GX280 desktop. I have added two additional 3com network cards but the install does not seem to see them, I have the Broadcom onboard as the only interface available. Is it possible to add any further packages to the install to add support for the 3com cards?
I would like to add Pfsense as a second router that would sit behind my existing TPLink WDR4300. This is set up as a DHCP server and assigns addresses in the 192.168.1/24 range, I am keen to utilise the firewall of pfsense so any general advice on how I could do that with keeping my existing router would be most welcome.
Thank you.