Sharing DSL internet with LAN

I want to setup my college LAN to access internet through a DSL modem provided by the ISP. I have an 1841 Cisco router with 2 FE interfaces, a couple of switches, 3Com and Netgear, a server (DHCP, Domain Controler, DNS). My setup of hardware is more like this:
ISP——>(RJ11)modem(RJ45)—->Router(FE)—->Switch—–>LAN(of which a server is part of).

I have a Redhat server which i also want to use as a Proxy server for this setup, nw i’m confused with what to config. My LAN uses 10.10.0.0 255.255.0.0 IPs and my modem has 168.167.154.95 for public.