If your laptop is already connected to the Internet through your wireless router, it's a simple matter of changing some settings in both computers to allow file and prionter sharing between the two. First, make sure that the network is secure with a strong, preferably WPA, security key then in each machine, go into Control Panel.
In XP look for Network Setup Wizard and in Vista or Windows 7, open the Network and Sharing Centre. The XP Wizard is easy enough to follow but Windows 7 is slightly more complicated - give the Homegroup a miss. Which operating systems are you using?