Ensure that the X220 physical wireless switch is turned On.
Hold Fn + F5 to enable Wireless (Ensure that the Status is showing On)
Click on the Wireless Icon on the lower right side of the taskbar to launch ThinkVantage Access Connections.
In Access Connections, select the Wireless SSID you want to connect to. Enter the password of the wireless network if prompted.
Once there is a green pulsing animation on the router icon, it means that the wireless has been successfully connected.
If there is no Wireless switch displayed on screen when pressing Fn + F5, please ensure that the hotkey and wireless drivers are installed. Verify the wifi driver through device manager. (make sure there is no yellow (!) bang on the wifi device) Visit the Lenovo support page to download the driver or use ThinkVantage System Update to download the drivers automatically.
Note: If there is no wireless capability at all, then use the built in wired ethernet to connect to the internet for purposes of running system update, or manually downloading and installing updated wifi drivers as part of troubleshooting.