Internet access in WAN environment

I’m trying to setup internet access for a New York office. Our main office is in Dallas (using TCP/IP scheme 192.168.90.xxx) which is connected to the internet via a Cisco router with NAT enabled. Currently, our New York office (192.168.100.xxx) comes down a Frame Relay pipe and out our Cisco router to get to the internet. I want to setup a router in New York so that users there don’t have to come down to our network to get to the internet. I setup a router and made it the default gateway on a workstation there, but it can’t find it. Any suggestions?