First Timer Wanting to create Home Router out of a pc.

[Volwarf]

Hi I am quite new to things like OPNSense and other similar operating systems. I currently use a tp link router with a customer firmware on it similar to DDWRT as my router. I have a old quad core pc with two Ethernet Ports, One onboard and the other a TP-Link Ethernet Card. So it has 2 ethernet ports. I want to get OPNSense up and running on that PC,

However I am not sure where to start because I want this pc to basically take over everything my router currently does but the router itself has multiple ethernet ports so I have a few pcs connected to it,

So what I am wonder is where do I start, Would I just set up the router to be a switch then have that plugged into the WAN interface on the pc with OPNSense on it.

I want to be able to have a secure router with all the advanced features OPNSense has to offer but I just am not sure where to start when it comes to figuring out how to set everything up.

If anyone could give me some pointers I would truly appreciate it.

Thank you for reading my post.

[Demusman]

Get Opnsense running.
Connect the LAN interface to a switchport on the old router.
You can now use the other switchports as needed.

On the old router you have to disable the dhcp server and assign it an IP in the subnet of the opnsense LAN so you can still access it's GUI.
You don't use the WAN port on the old router.

[Volwarf]

Thank you, that makes sense.