First check that you have Wifi on and the location you are in has a strong connection. To enable Wif, click the Network button on the start bar and make sure that Wifi is highlighted and Airplane mode is not. If this is the case and you still cannot connect, try running the Windows connection troubleshooting tool found in Control Panel > Network and Internet > Network Connections. Right click the Wifi device and select Diagnose. The troubleshooter will walk you through the steps to connecting to the internet. If that fails, go to the [http://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/yoga-series/yoga-900-13isk2|Lenovo product page] and download and reinstall the Wifi drivers.