 ali_ahsan, To turn on the wifi you would press the F2 key or FN+F2. You can also go into the mobility center in the control panel to turn the wifi on as well.
what to do?
wifi 1704 802 1.1 ... is not working after udating window to 8.1, enabled but 
showing a red cross icon on adopter icon. when troubleshoted showed that wifi 
compatibility is turned off