Can not connect to the internet using wireless network interface?

My son has a Advent 7087 laptop and he can connect to the internet using an ethernet cable, but when he tries using the wireless network interface he gets the following message:
NO WIRELESS NETWORKS WERE FOUND IN RANGE.
MAKE SURE WIRELESS SWITCH ON YOUR COMPUTER IS ON.
WIRELESS NETWORK INTERFACE DISABLED
Could you please tell me how to enable the network and where it is found in windows.