the "Fn" key is usually orange accented, for all the orange functions. it stands for "function". make sure you are holding that function button down and press the button with the wifi tower or logo on it (usually on the F1-F12 keys at the top of the keyboard".
there might also be a physical toggle switch, that clicks on and off, look around the base of the laptop for something like that.
lastly go into control panel, network settings, and make sure its "enabled"
look into windows updates and virus etc.
without more details the troubleshooting process is vague.