The laptop should have a built in adapter, just switch it on from the external switch and it will pick up networks. However, you should configure your router with security. I have WPA protection and a passkey as well as a MAC filter. Basically the MAC filter only allows PCs with the MAC you enter to connect to your network.
Yeah this works but you can also protect your connection by using a WEP setting which requires you to enter a code to access the signal the code is usually located on your router