1) Check your wireless switch. It should be turned ON. It can be on your keyboard or it can be a special dedicated button apart from the keyboard.
2) Go to your PC Settings, then to the Wireless Tab and make sure that the Airplane Mode is set to OFF and WiFi is set to ON.
3) Check your drivers for WiFi. Go to Device Manager. If it is showing a caution sign besides your WiFi driver, it means that your driver is faulty, corrupted or not correctly installed. Obtain the latest driver version from your WiFi Device/Computer manufacturer and install it. Then turn WiFi ON in Network Settings.