Configuring help on how to allow a specific ip to acces my lan.

Here is my network configuration, for a setup , now i need to connect
We are running a server software to control client pc, and server pc is connected to internet using a modem and sharing server internet connection using inbuild w7 ICS.
now we need to connect to client pc for sharing server pc’s resource and also controlling them.
here is what i want to do,
Please help me.
Thanks in advance.

server-pc-----hap lite-----Client-pc1
server-pc-----hap lite-----Client-pc2

Adding diagram for more explanation please help me.