How does inserting internet into the SWiM System Work?

Ok, so I just got installed with HR24 in the LV Rm and H24 in the Bedroom. I also have a D12, but it should be good to go. My theory is this: The DECA is already built into the H24 and HR24. Is there a way to plug in ethernet/internet into the rear of either of these ird's and have it route to the other by way of the built in DECA? Or do I have to have a DECA adapter to insert the internet signal somewhere along the line? And, if so, can this be done at any location i.e. the D12 that is in the office and has the router next to it?

Thanks guys.