Static Routes?

I realize the solution to this issue probably does not reside on the AC66 side but thought someone here might have good advice anyhow...

I've configured two independent networks on a D-Link 2540B - 4 LAN port ADSL modem (IP at 198.162.1.2). The first interface is bridged DSL and serves only modem LAN port 1 connected to an AC66 WAN port. The second interface is configured as PPPoE serving modem LAN ports 2, 3 and 4 - Each connecting wired devices to my DSL. DHCP is modem managed ON for the second network with a 192.168.1.241 to 192.168.1.254 range.

Both networks work fine but independent of one another. I believe this is as intended by D-Link for their "Port Mapping" feature which I used to setup the two networks. Taking this two network approach allowed me to fully use all LAN ports of the modem and still provide a bridged connection to the AC66.

AC66 details; IP at 198.162.1.1, DHCP ON for 198.162.1.5 to 198.162.1.240 range. Some hosted devices have static IPs, eg Printer is fixed at 198.162.1.102, NAS is at 198.162.1.103, etc.

So the question is;
Anyone know how to create a "Static Route" that would allow me to link the AC66 clients and D-Link wired LAN network?
For instance, I would like a wired client on modem LAN port 3 to be able to access the AC66 managed Printer or NAS.

(FWIW, D-Link technical support is useless. Can't get them on the phone and via eMail they pass the buck to ASUS)