One Buillding 2 different IP Segment

Hi all,

Currently my office is a single LAN Segment. Since we are expanding with more users coming in, so there is a need to create another LAN segment which can communicate in terms of server access, network sharing and internet. I have cisco 2600 configured to enable these new segment. It works internally fine but i have one problem. What should i do to connect these new segment to my firewall located at existing segment? do i have to do some port forwarding here?