If you're using an access point such as a router, you will need to log-in to the administration interface. You can do this with the help of a browser but in order to do that you'll need to find the IP of the router. Go to Start > Run > cmd > type ipconfig|findstr Gateway then use the IP and paste it into a browser address bar. You will be asked for a username and password. Usually admin/admin is the right combination. If that's not the combination, consult the manual. Once you are in the admin interface, go to Wireless > Security.