Okay, here it is. Addresses are my own, of course you would change them to whatever you wanted on your LAN:

Main menu.
Setup menu.
Network configuration.
External Adapter 1.
Configuration: Manual.
IP address: 192.168.1.4
Subnet mask 255.255.0.0 (I do this special so two local subnets can both reach the Central)
Defailt gateway: 0.0.0.0
Serve receiver units: Checked.
Use this adapter for internet lookup: Checked.

AT THIS POINT pressing the down arrow button one more time will get you to the RECEIVERS... button. Press the right arrow button and BOOM, you're in the screen you couldn't find before. On mine I'm set to:
First address: 192.168.1.90
Last address: 192.168.1.99
Subnet mask: 255.255.0.0
DONE.