2 IP Addressess

We are having network of 13 W 98 clients running on a NT4 network. We used dial up to access internet and proxy server for the clients. Now the company is providing internet from their server to our premesis by a 10 baseT cable. They are also givingus a static IP Address.
We dont know where to connect the cable in our HUB. If we configure any of our PC with their IP then that PC is out of our network. How can two IP address co-exist.