There should be a hot key for this, check you laptop's manual. If you cannot find the manual, click "My Conmputer", "Control Panel", "System" "Hardware Device", find wireless adaptor, right click then you can swtich it on/off.
This is not the main problem. You need to get into set up of your Router (LiveBox in this case). Router shold be setted up with "MAC Address Filtering", otherwise everyone in your street can access your router. It means it only allows certain device connect with it. Now you need to find MAC address on your laptop and add into the list. You also need to put wireless network's SSID into you laptop's wireless setup. If the router use encryption, laptop should be set up to use the same encryption key.
Clear now? Maybe not, just do one thing at a time.