How to activate wi-fi?

Hello,
I recently shutdown my Acer Aspire 4520- laptop, and when I restarted the computer it would not pick up the wi-fi router. I ran Windows to see what the problem is and it said the wi-fi switch needed to be turned on. My computer does not have an external switch. You must go pc mobility to turn the switch on but it will not turn on. Do not have a clue what to do.