Cisco routers support static and dynamic routing, and there are more than one way to configure these routes.  This HowTo describes a way to configure a static route.  Say you have installed a VPN Appliance to connect your network to a business partner's network.  Your network uses the 10.0.0.0/8 private addressing scheme, thus allowing you to use any valid IP address within the 10.x.y.z address range.  Your router has been assigned the IP address of 10.0.0.1. 

Your new business partner uses addresses in the 192.168.0.0/16 network, allowing them to use any valid IP address in the 192.168.y.z address range.  They have provided you with a VPN appliance that you connect to your network and assign the local address of 10.9.0.99. 

You need to tell your router at 10.0.0.1 that the 192.168.0.0/16 network is accessible through 10.9.0.99.