How to turn on,changing wireless capability which is turned off?

First of all I would like you to check that whether all parts are functioning properly or not, if every other part is functioning properly then its fine else if any component is disturbed then you just need to check that whether your computer is affected by virus or not and there are chances that virus can also create problem in normal functioning of any system so if you are not using any antivirus try to use some of them to protect your computer.

In most of the computers we have direct switch for wireless which is almost present near the on/off switch of laptop so try to press that switch on and check whether it is working properly or not because normally it changes its color when we turn it on and if it has any problem then for this you have to consult your customer care support. And if is working properly then you just try to make a search from you computer only for network and if you find that it is capable of searching network then you can assure that your network wireless is switched on and is functioning properly. And do check that your network is not protected with any password because that won't let you connect unless you will provide password. If again you are having problem then better take your system to customer care where they will support to their extent,Dell customer support can help you by coming to your way only so you don't have to move around.