In general (because there are many different Netgear routers), go into the router's settings by typing 192.168.0.1 (or possibly 192.168.1.1) into your web browser. You will be promoted for the router's Username & Password which should be in a label on the underside of the router. Once in, go to the Wireless Settings where you should be able to set up security. Ideally, you want to use WPA2 or at least WPA. Create a "key" of between 8 and 63 characters (which can include spaces). Remember your key because it needs to be entered when connecting any computers "wirelessly".