1. On your laptop, go to command line, ping your desktop computer name that is connecting to the router, if get the IP, then your wireless connection is ok
2. On your desktop, go to your router's admin page, (maybe 192.168.0.1, refer to your user manual), then assign a IP address for your laptop.
3. On your laptop, configure the network settings to let it use the IP that was assigned by the desktop, and the subnet, etc.