First ensure the WiFi adapter inside your laptop is enabled (wireless symbol at top edge of keyboard should be lit).
Go to Control Panel > Network & Sharing Centre applies to Control Panel set to 'Icon' view, not 'Category' view).
In the main panel, click "Connect to a network"
From the list of available networks, click on yours and you'll be prompted to enter the wireless security key (often referred to as the wireless password).
Click "Connect" and your laptop hopefully will get connected to the router provided it is not too far away from it to get a good wireless signal.