Go to your network connections (Not sure what version of windows you have) but eventually you need to get to your connection list (Wired or wireless, in your case wired). Right click on which ever wired port (Local Area Connection) your using and open up the properties. Click on the IPv4 and view the properties of that and assign the router an IP address. Since your not using a subnetting scheme, leave it as 255.255.255.0 and the default gateway is your router's IP address (in this case though, I believe it would be the IP of your laptop)